Constructive Empiricism

First published Wed Oct 1, 2008; substantive revision Wed Jul 30, 2025

Constructive empiricism is the version of scientific anti-realismpromulgated by Bas van Fraassen in his famous bookThe ScientificImage (1980). Van Fraassen defines the view as follows:

Science aims to give us theories which are empirically adequate; andacceptance of a theory involves as belief only that it is empiricallyadequate. (1980, 12)

With his doctrine of constructive empiricism, van Fraassen is widelycredited with rehabilitating scientific anti-realism. There has been acontentious debate within the philosophy of science community overwhether constructive empiricism is true or false. There is also someunclarity regarding what van Fraassen’s arguments for thedoctrine actually are. In addition, there are controversies about whatthe doctrine actually amounts to. While constructive empiricism hasnot gained a wide number of adherents, it continues to be a highlyinfluential doctrine in philosophy of science.

1. Understanding Constructive Empiricism

1.1 Contrast with Scientific Realism

Constructive empiricism is a view which stands in contrast to the typeof scientific realism that claims the following:

Science aims to give us, in its theories, a literally true story ofwhat the world is like; and acceptance of a scientific theory involvesthe belief that it is true. (van Fraassen 1980, 8)

In contrast, the constructive empiricist holds that science aims attruth about observable aspects of the world, but that science does notaim at truth about unobservable aspects. Acceptance of a theory,according to constructive empiricism, correspondingly differs fromacceptance of a theory on the scientific realist view: theconstructive empiricist holds that as far as belief is concerned,acceptance of a scientific theory involves only the belief that thetheory is empirically adequate.

1.2 On Literalness

Even given her stance about what theory acceptance involves, aconstructive empiricist can still understand scientific theoriesliterally. What makes for a literal understanding of a theory? Whilevan Fraassen does not offer a full-fledged account of literalness inThe Scientific Image, he does offer the following twonecessary conditions for a theory’s being understoodliterally:

The theory’s claims are genuine statements capable of truthor falsity.
Any literal construal of a theory cannot change the logicalrelationships among the entities claimed by thetheory—“most specifically, if a theory says that somethingexists, then a literal construal may elaborate on what that somethingis, but will not remove the implication of existence” (1980,11).

In insisting on an understanding of scientific theories as literallytrue, the constructive empiricist sides with the scientific realistagainst conventionalists, logical positivists, and instrumentalists.While advocates of these latter positions may take scientific theoriesto be true, they do so only by interpreting those theories innon-standard ways—in ways that, for instance, violate (1) or (2)above.

1.3 Contrast with Logical Positivism

One of the reasons constructive empiricism is viewed as significant isthat it carries on the tradition of the logical positivists withoutbeing saddled with the problematic aspects of the positivists’positions. The constructive empiricist follows the logical positivistsin rejecting metaphysical commitments in science, but she parts withthem regarding their endorsement of the verificationist criterion ofmeaning, as well as their endorsement of the suggestion thattheory-laden discourse can and should be removed from science. Beforevan Fraassen’sThe Scientific Image, some philosophershad viewed scientific anti-realism as dead, because logical positivismwas dead. Van Fraassen showed that there were other ways to be anempiricist with respect to science, without following in the footstepsof the logical positivists.

1.4 A Doctrine about Aims

Constructive empiricism has the look of an epistemological view aboutwhat one should believe—namely, that one should be agnosticabout the claims about unobservables that our scientific theoriesmake. But the view is not intended to be read in that way.Constructive empiricism is to be understood as a doctrine about whatthe aim of science is, not a doctrine about what an individual shouldor shouldn’t believe.

To make this clear, we can, following van Fraassen (1998, 213), makethe following terminological distinction:

scientific agnostic: someone who believes the science s/heaccepts to be empirically adequate but does not believe it to be true,nor believes it to be false.
scientific gnostic: someone who believes the science s/heaccepts to be true.

It’s clear, in light of this distinction, that one can be ascientific gnostic and a constructive empiricist—one wouldsimply choose to have beliefs that go beyond what science is aimingat. There is, of course, a connection between the scientificrealist/constructive empiricist dichotomy and the scientificgnostic/scientific agnostic dichotomy:

Scientific realists think that the scientific gnostic trulyunderstands the character of the scientific enterprise, and that thescientific agnostic does not. The constructive empiricist thinks thatthe scientific gnostic may or may not understand the scientificenterprise, but that s/he adopts beliefs going beyond what scienceitself involves or requires for its pursuit. (van Fraassen 1998,213–214)

A final point to make about aims is that the constructive empiricistdistinguishes between the aim of an individual scientist or group ofscientists (which may be fame, glory, or what have you) and the aim ofscience itself. The aim of science determines what counts as successin the enterprise of science as such (van Fraassen 1980, 8). Becauseconstructive empiricists do not identify the aim of science withwhatever goals the majority of scientists may have, they deny thatconstructive empiricism is a thesis in sociology subject to the kindof empirical confirmation or disconfirmation any scientific thesisfaces. Instead, constructive empiricism is to be understood as aphilosophical description of science that seeks to explain how anempiricist can regard the activity of science as consistent with theempiricist’s own standards of rational activity. Like theinterpretation of any human activity, constructive empiricism isconstrained by the “text” of the scientific activity itinterprets. Within those constraints, it succeeds or fails accordingto its ability to provide an interpretation of science thatcontributes to our understanding of science, making intelligible to usvarious elements of its practice. (van Fraassen 1994,188–192)

The success, then, of constructive empiricism as an account of sciencedoes not depend on how science is understood or undertaken by actualscientists. Still, one might start to question the empirical adequacyof constructive empiricism’s interpretation of science if theaccount wasdramatically at odds with the attitudes andpractices of actual scientists. Fortunately, then, for the defender ofconstructive empiricism, recent evidence indicates that is not thecase. Based on a methodical survey of practicing scientists, Beebe andDellsén (2020, 359–361) suggest that the attitudes ofcontemporary scientists are largely in line with the constructiveempiricist’s views of theory acceptance and science’saims.

1.5 Empirical Adequacy

Here is a rough-and-ready characterization of what it is for a theoryto be empirically adequate:

a theory is empirically adequate exactly if what it says about theobservable things and events in the world is true—exactly if it‘saves the phenomena.’ (van Fraassen 1980, 12)

A sufficiently unreflective constructive empiricist might adopt thisconstrual of empirical adequacy for her theory, but a moresophisticated constructive empiricist would probably embrace anaccount of empirical adequacy akin to that which van Fraassen developslater inThe Scientific Image.

To understand that account, one needs first to appreciate thedifference between thesyntactic view of scientific theoriesand van Fraassen’s preferredsemantic view ofscientific theories. On the syntactic view, a theory is given by anenumeration of theorems, expressed in some one particular language. Incontrast, on the semantic view, a theory is given by the specificationof a class of structures (describable in various languages) that arethe theory’s models (the determinate structures of which thetheory holds true). As van Fraassen says,

To present a theory is to specify a family of structures, its models;and secondly, to specify certain parts of those models (the empiricalsubstructures) as candidates for the direct representation ofobservable phenomena. (1980, 64)

A theory is empirically adequate, then, ifappearances—“the structures which can be described inexperimental and measurement reports” (1980, 64)—areisomorphic to the empirical substructures of some model of the theory.Roughly speaking, the theory is empirically adequate if the observablephenomena can “find a home” within the structuresdescribed by the theory—that is to say, the observable phenomenacan be “embedded” in the theory. See Figure 1 for agraphical illustration of the relations that make a theory empiricallyadequate on van Fraassen’s view, with the cloud shapesrepresenting the relata of the isomorphism relation.

A cloud shape labelled 'Appearances' connected to a network of shapes by an arrow labelled 'isomorphic'. The network of shapes has squares, a plus sign, a star, a half-circle, and a cloud shape labelled 'Empirical substructures'. The network of shapes is labelled 'A Model of a Theory'.

Figure 1. A Theory’s EmpiricalAdequacy

This conception of a theory’s empirical adequacy is arguablywhat allows a constructive empiricist to avoid the kind of doxasticcommitment Friedman (1982, 278) and Rochefort-Maranda (2011,61–62) describe as posing a problem for the constructiveempiricist (a problem that Rochefort-Maranda subsequently attempts tosolve). Here is that problem:

Since we might initially think that sentences about observables are,according to a theory, equivalent to certain sentences aboutunobservable entities, we might also think that commitment to beliefin the existence of the observables undesirably commits theconstructive empiricist to the existence of the correspondingunobservable entities. (And so correspondingly, agnosticism about theunobservables undesirably commits the constructive empiricist toagnosticism about the equivalent observables.)

The constructive empiricist arguably dissolves this problem byinvoking the above conception of empirical adequacy.(Rochefort-Maranda gestures in the direction of, but does notexplicitly describe, this dissolution in his footnote 1.) Belief thata theory is empirically adequate amounts to the belief that theobservables can be properly embedded in at least one of thetheory’s models. Belief in the possibility of that embeddingdoes not require the constructive empiricist to take the truth ofsentences about observables to entail the truth of sentences aboutunobservables. By taking a theory to be empirically adequate, theconstructive empiricist is simply saying that the phenomena we observe(and believe to exist) can exist within the structure the theorydescribes, without additionally being committed to saying that theunobservable parts of that theoretical structure are parts of theactual structure of the world.

Note that the phenomena relevant to a theory’s empiricaladequacy are all actual observable phenomena (1980, 12). Sofor a theory to be empirically adequate, it has to be able to accountfor more than just the phenomena that have actually been observed andthe phenomena that will be observed. SeeSection 3.4 below for a discussion of the worry that the constructiveempiricist’s belief in the empirical adequacy of her acceptedtheories thereby extends beyond what a bona fide empiricist ought tobelieve.

1.6 What’s Observable

Insofar as the empirical adequacy of a theory amounts to theembeddability of observable phenomena within substructures of thetheory’s models, the constructive empiricist’s account ofempirical adequacy rests heavily on the distinction between what isobservable and what is not. If, as it is natural to think,‘isobservable’ is a vague predicate, we should not expect there tobe a precise demarcation between what’s observable andwhat’s unobservable. Observability can still serve as a usefulconcept in the philosophy of science, as long as there are clear casesof observability and clear cases of unobservability.

Here is one rough characterization of observability:

X is observable if there are circumstances which are suchthat, ifX is present to us under those circumstances, thenwe observe it (van Fraassen 1980, 16).

For the constructive empiricist, this characterization is “notmeant as a definition, but only as a rough guide to the avoidance offallacies” (van Fraassen 1980, 16). It is important to clarifythat, as a constructive empiricist would use the terminology, one onlyobserves something when the observation isunaided. One doesnot see cells through a microscope; instead one sees an image, animage which the scientific gnostic understands one way but thescientific agnostic understands a different way.

Note that the observability of interest is relativized to“us,” the members of the epistemic community whosescientific theories are the topic of interest. Since what counts asobservable is relative to what epistemic community the observer ispart of, and since the members of that epistemic community are thesubject of scientific theory, the constructive empiricist takes whatcounts as observable as the subject of scientific theory and notsomething that can be determined a priori (van Fraassen 1980,56–59). Science itself, then, is ultimately the arbiter of whatcounts as observable. For worries about circularity in the use ofaccepted scientific theory to determine which parts of the world areobservable (and hence to determine which theories of science areempirically adequate and thereby candidates for acceptance), seeSection 3.8 below.

1.7 Acceptance

Acceptance has both an epistemic and a pragmatic component. When oneaccepts a theory, one has a belief, and also a commitment. The beliefis that the theory is empirically adequate. The commitment is “acommitment to the further confrontation of new phenomena within theframework of that theory, a commitment to a research programme, and awager that all relevant phenomena can be accounted for without givingup that theory” (1980, 88). According to the constructiveempiricist, this commitment is made at least in part on pragmaticgrounds: there is an important role for non-epistemic values in theorychoice (van Fraassen 2007, 340).

For the constructive empiricist, acceptance comes in degrees. This caninfluence how one engages in discourse in the domain of thetheory:

If the acceptance is at all strong, it is exhibited in theperson’s assumption of the role of explainer, in his willingnessto answer questionsex cathedra. (van Fraassen 1980, 12)

Van Fraassen goes on to explain that acceptance produces contextswhere one engages in discourse “in a context in which languageuse is guided by that theory.”

One reason the constructive empiricist’s account of acceptanceis important is that it allows us to make sense of scientificanti-realists such as constructive empiricists (of the scientificagnostic variety) talking as if a particular theory is true. When onelooks at scientific discourse, this is what scientists are oftendoing: they treat a theory as if they fully believe it, and answerquestions and give explanations using the resources of the theory. Theconstructive empiricist can account for this behavior, withoutattributing full belief in the theory to the scientists, by describingthe scientists as merely accepting, without fully believing, thetheories they develop (van Fraassen 1980, 81–82).

The constructive empiricist can acknowledge that scientific realistsalso recognize that there is a pragmatic dimension to theoryacceptance. But “because the amount of belief involved inacceptance is typically less according to anti-realists, they willtend to make more of the pragmatic aspects” (van Fraassen 1980,13).

2. Arguments For Constructive Empiricism

2.1 Poor arguments for constructive empiricism

Before turning to stronger arguments for constructive empiricism, itwill be helpful to draw attention to a couple scientific anti-realistarguments that the constructive empiricist would be well-advised notto use in support of her view.

First, consider the Argument from Underdetermination. This argumentstarts by pointing out that for any theory, there are rival theoriesthat are empirically equivalent to it—the theories make all thesame predictions about what’s observable, but differ only withregard to what’s unobservable. The argument goes on to say thatit follows that all the empirically equivalent theories are equallybelievable, and hence belief in the truth of any one of thoseempirically equivalent theories must be irrational.

While the constructive empiricist view is a view about the aims ofscience and not a normative theory in epistemology, the constructiveempiricist is an individual who values the sort of epistemic modestywhich might motivate one to harbor anti-realist sympathies in general.To the extent that the constructive empiricist embraces epistemicmodesty, she might also be an epistemic voluntarist, a person whobelieves that “rationality is only bridled irrationality”(van Fraassen 1989, 172). Any behavior that does not make oneinconsistent or incoherent is rational, by the voluntarist’slights. Such an attitude might seem the natural epistemic one for theconstructive empiricist to hold, insofar as the constructiveempiricist is impressed by the cognitive limits that prevent us fromhaving conclusive evidence in favor of any one particular theory.

One reason the constructive empiricist would be well-advised not toembrace the Argument from Underdetermination, then, is that it goesagainst a voluntarist position in epistemology. (This point is clearlymade by Van Dyck 2007, 19–22, and agreed to by van Fraassen2007, 347.) By the voluntarist’s reckoning, going beyond theevidence to the extent that one chooses to believe in the truth of atheory, both in its observable and unobservable aspects, could verywell be rational.

The relatively permissive epistemological view of a constructiveempiricist who is also an epistemic voluntarist helps explain why sucha constructive empiricist would be prudent not to take constructiveempiricism to be a normative theory concerning the deliverances ofscience. Mistakenly understood in that normative way, constructiveempiricism would imply that belief in a theory’s empiricaladequacy is the only rational candidate for the belief involved in atheory’s acceptance. Such a constraint on the rationality ofopinion is clearly at odds with any epistemic voluntarism theconstructive empiricist might embrace.

Gideon Rosen (1994, 160–161) gives another reason that theconstructive empiricist ought not accept underdetermination argumentsas grounds for constructive empiricism. Consider the following twohypotheses:

T is empirically adequate—i.e.,T isadequate to all observable phenomena, past, present, and future.
T is adequate to all phenomena observed so far.

As Rosen notes, one’s current evidence does not tell in favor ofeither hypothesis over the other. So by an underdetermination-styleargument, one is not justified in believing either hypothesis. Butbelief in (A) is the belief the constructive empiricist contends isinvolved in theory acceptance. (For more on how one might takeRosen’s argument as an argument against constructive empiricism,seeSection 3.4 below.)

The second scientific anti-realist argument a person would bewell-advised not to use in support of constructive empiricism is thePessimistic Induction Argument. This argument points out thatscientific theories in the past have been shown to be false, so byinduction, we should think that current theories are false, too. Ifthis argument is taken to have the conclusion that belief in ourcurrent theories is irrational, then, as above, the argument isincompatible with any voluntarism the constructive empiricist mightembrace. The argument is also incompatible with the view of aconstructive empiricist who, in the skeptical spirit of anti-realistviews in general, rejects reasoning based on a principle of induction.Van Fraassen, for instance, writes: “I do not think that thereis such a thing as Induction, in any form” (2007, 343).

2.2 Empirical Adequacy versus Truth

So how might one argue for constructive empiricism? One argument forconstructive empiricism hinges on the fact that belief in theempirical adequacy of a theory is less epistemically audacious thanbelief in the truth of the theory. Both beliefs, of course, go beyondthe evidence:

In either case we stick our necks out: empirical adequacy goes farbeyond what we can know at any given time. (All the results ofmeasurement are not in; they will never all be in; and in any case, wewon’t measure everything that can be measured.) (van Fraassen1980, 69)

So why is belief that a theory is empirically adequate preferable tothe belief that the theory is true? Van Fraassen famously and pithilyputs the point as follows:

it is not an epistemological principle that one might as well hang fora sheep as for a lamb. (1980, 73)

The constructive empiricist rejects arguments that suggest that one isrationally obligated to believe in the truth of a theory, given thatone believes in the empirical adequacy of the theory.

For this epistemological argument to work, the distinction betweenempirical adequacy and truth has to be well-founded. A significantpart ofThe Scientific Image is devoted to that task. Asdescribed inSection 1.6, the constructive empiricist argues that one can make sense of theobservable/unobservable distinction, even if observation istheory-laden. (If the distinction between observables andunobservables didn’t make sense, the concept of empiricaladequacy would be incoherent.)

Rosen (1994, 161–163), as well as Monton and van Fraassen (2003,407–408), offers an additional rationale for the constructiveempiricist’s embrace of empirical adequacy rather than truth asthe hallmark of the belief component of theory acceptance. One mightreasonably think of belief in the empirical adequacy of acceptedtheories as the weakest attitude one can attribute to scientists atthe same time that one is still able to make sense of their scientificactivity. At the same time, belief in the empirical adequacy of atheory is sufficiently cautious as to allow the believer to remainfaithful to the spirit of empiricism. Thus, constructive empiricism isa view which allows one to regard the activity of science as activitythe empiricist can safely endorse.

Belief in empirical adequacy as too strong a criterion for acceptance?

One worry for the constructive empiricist is that theory acceptancecan be had under conditions that do not require belief in theempirical adequacy of the accepted theories. As Healey 2019 pointsout, scientists appreciate that many of our best scientific theoriesare not able properly to account for all the observable phenomena theyare meant to account for; the theories are not, in fact, entirelyempirically adequate. Scientists nevertheless accept those theories:they treat them as working hypotheses to use in the undertaking oftheir work, and (as van Fraassen 1980, 88, suggests) the scientistsare committed to confronting new empirical phenomena in the frameworkthose theories offer. If, then, we understand theory acceptance in theway the constructive empiricist does, we must take thescientists’ acceptance of these theories as misplaced, since thescientists do not believe the theories to be empirically adequate.

One initial response the constructive empiricist might offer to thischallenge is the following: if the scientists truly believe thetheories to be empirically inadequate, they are not actually acceptingthe theories, after all. A more sophisticated reply the constructiveempiricist might give invokes the recognition that, as § 1.7above notes, acceptance comes in degrees and has a pragmatic element.The constructive empiricist can allow that a scientist (mostly)accepts a theory, insofar as:

the scientist believes that many/most of the observable phenomena itdescribes can be embedded in the theory’s substructures, and
the scientist is fairly strongly committed to using the theory as thebasis for the scientist’s research program.

The satisfaction of (1) and (2) suffice for the scientist to acceptthe theory to a high degree, even if the scientist does not accept thetheory in a categorical, unqualified way. As van Fraassen himselfacknowledges, it is onlyunqualified acceptance of a theorythat involves the belief that the theory is empirically adequate(1998, 213).

Any tendency we might have to think scientistsdo fully accepttheories may simply be the result of the social role the scientistsplay as explainers of those theories (as also noted in § 1.7above). In that role, the scientists “answer questionsexcathedra ” (van Fraassen 2007, 12), in a manner that theunsophisticated listener might mistakenly perceive as a display ofunqualified confidence in and acceptance of the theories’empirical adequacy. The reality is more subtle—the acceptance isalmost always a qualified one.

In any case, even if there is disagreement about how fully scientistsaccept theories, the above reflections suggest that the constructiveempiricist’s position on theory acceptance is vindicated: thedegree to which scientists accept a theory is plausibly correlatedwith the degree to which they believe the theory to be empiricallyadequate.

2.3 The Relationship Between Theory and Experiment

The constructive empiricist argues that constructive empiricism“makes better sense of science, and of scientific activity, thanrealism does” (van Fraassen 1980, 73). The constructiveempiricist can be understood as giving two arguments for this claim;the first argument will be presented here, and the second argumentwill be presented in the next subsection.

Constructive empiricists might maintain that, for working scientists,the real importance of scientific theories is that they are a factorin experimental design. They contrast this with the traditionalpicture presented by philosophy of science. According to thetraditional picture, the main goal of scientific practice is todiscern the fundamental structure of the world, and experimentationsimply is used to determine whether theories should be taken to betrue, and hence as contributing to our knowledge of the fundamentalstructure. The constructive empiricist, in contrast, suggests that thereason a scientist turns to a theory is that experimental design isdifficult, and theories are needed to guide experimental inquiry. Butwhat scientists are really aiming to discover, according to theconstructive empiricist, are “facts about the world—aboutthe regularities in the observable part of the world” (vanFraassen 1980, 73).

Van Fraassen argues for this position in part by describingMillikan’s famous experiment measuring the charge of theelectron. Scientific realists take this experiment to be making adiscovery about the nature of the unobservable entities known aselectrons. Van Fraassen, in contrast, presents the experiment as“filling in a value for a quantity which, in the construction ofthe theory, was so far left open” (1980, 77). In doing theexperiment, Millikan was discovering a regularity in the observablepart of the world, and was providing a value for a quantity in atomictheory. Millikan need not be understood as discovering something aboutthe nature of unobservable objects in the world. Van Fraassen saysthat in a case like Millikan’s,

experimentation is the continuation of theory construction byother means. The appropriateness of the means follows from thefact that the aim is empirical adequacy. (1980, 77)

2.4 The Pragmatics of Theory Choice

Another way in which, according to the constructive empiricist,constructive empiricism makes better sense of science than realismdoes has to do with theory choice. Some virtues that scientists see intheories are pragmatic virtues, not epistemic virtues. This shows thatscientists are choosing between theories using criteria other thantruth.

What virtues are pragmatic? Here is what van Fraassen says:

When a theory is advocated, it is praised for many features other thanempirical adequacy and strength: it is said to be mathematicallyelegant, simple, of great scope, complete in certain respects:also of wonderful use in unifying our account of hithertodisparate phenomena, and most of all, explanatory. (1980, 87)

Some scientific realists might hold that some of these are epistemicvirtues, not pragmatic virtues. With regard to simplicity, theconstructive empiricist can recognize that scientific realistssometimes hold that simpler theories are more likely to be true, butat the same time the constructive empiricist can contend that

it is surely absurd to think that the world is more likely to besimple than complicated (unless one has certain metaphysical ortheological views not usually accepted as legitimate factors inscientific inference). (1980, 90)

With regard to explanation, constructive empiricists recognize thatscientific realists typically attach an objective validity to requestsfor explanation (van Fraassen 1980, 13), but constructive empiricistsdo not grant that objective validity. Van Fraassen’s argumentsthat explanation is pragmatic constitute a significant part ofTheScientific Image, and will be discussed in the nextsubsection.

Constructive empiricists recognize that these pragmatic factors likesimplicity and explanatory power are important guides in the pursuitof the aim of science (van Fraassen 1980, 89). But they insist thatthese factors are valuable in that pursuit only insofar as theirconsideration advances the development of theories that areempirically adequate and empirically strong. The factors do not havespecial value as indicators of the truth of what the theories sayabout the unobservable parts of the world.

Ivanova 2024 points out that the correlation between the truth ofscientific theories, on the one hand, and various virtues such assimplicity, beauty, and unity, on the other, may be weaker than onemight initially suspect. As she suggests, there are aestheticallypleasing theories generally regarded as failures— for instance,the Kaluza-Klein theory that attempts to provided a unified account ofgauge fields— while there are also less aesthetically pleasingtheories that have been empirically successful— for instance,the Standard Model of particle physics (153–155).

Invoking the kind of study that Lombrozo 2007 undertakes, Ivanova 2024also emphasizes that as a matter of psychological fact, people tend tofavor simple hypotheses even when those hypotheses are less likely tobe true than more complex hypotheses (158–159). In Lombrozo2007, participants in an experiment expressed a preference for one oftwo hypotheses for describing the cause of symptoms in a patient: (i)a simpler one-disease-cause hypothesis D₁ or (ii) a morecomplex two-disease-cause hypothesis, (D₂ &D₃). It was only when the base rate of the conjunction ofthe two diseases in (D₂ & D₃) was describedasten times more likely than the base rate of thedisease in D₁ that a majority of the participants favoredthe more complex two-disease-cause hypothesis. This experimentalevidence suggests that preferences for simplicity in theory choice arethe result of pragmatic considerations and/or our psychologicalconstitution, rather than the result of any sensitivity we may have tothe supposed truth of a preferred simpler hypothesis.

2.5 The Pragmatics of Explanation

Scientific realists, by contrast, sometimes say that they believe inthe truth of scientific theories because the theories provide asatisfying explanation of the observable phenomena, an explanationthat unifies what would otherwise be disparate observations. Theconstructive empiricist is not moved by such considerations:

A person may believe that a certain theory is true and explain that hedoes so, for instance, because it is the best explanation he has ofthe facts or because it gives him the most satisfying world picture.This does not make him irrational, but I take it to be part ofempiricism to disdain such reasons. (van Fraassen 1985, 252)

Indeed, one can recognize the explanatory power of a theory withouttaking it to be true. Van Fraassen points out that theories canexplain well even if they are false. Newton’s theory ofgravitation explains the motion of the planets and the tides,“Huygens’s theory explained the diffraction of light,Rutherford’s theory of the atom explained the scattering ofalpha particles, Bohr’s theory explained the hydrogen spectrum,Lorentz’s theory explained clock retardation.” But none ofthese theories is now thought to be true.

For the constructive empiricist, the explanatory power of a theoryamounts to nothing more than the theory’s ability to providecertain bits of information in response to contextually definedqueries. Scientific explanation amounts to the highlighting of variousaspects of the structure postulated by the theory, to answer, in acontextually dependent way, various questions of interest to us (vanFraassen 1980, 124). Science, then, contributes nothing to explanationover and above the descriptive and informative content of thescientific theory: “a success of explanation is a success ofadequate and informative description” (van Fraassen 1980,156–157). Explanation cannot be reduced to that content, though,since explanation cannot occur unless an appropriate question, offeredin a particular context, is provided. Explanation thus goes beyondwhat science reveals to us. The constructive empiricist can henceavoid saddling scientists with a commitment to the unobservableentities invoked in such explanations, properly claiming that suchcommitments are not licensed by the activity of science. (See Kitcher& Salmon 1987 for the view that even if requests for explanationare contextually delimited, what counts as a good / relevantexplanation depends also on non-contextual factors.)

A fair portion of the constructive empiricist’s account ofscientific explanation is thus devoted to an explication of thecontextual dependence of explanation. Among other reasons given infavor of that contextual dependence, van Fraassen points out thatexplanations are typically causal in character—they attempt tosituate the event-to-be-explained in the “causal net”postulated by the scientific theory. Which events in that net arepicked out as “the” cause(s) of some event-to-be-explaineddepend upon the interests of the individuals asking the explanatoryquestion (1980, 124–126).

Explanation will frequently involve the invocation of counterfactuals,often of the form: if event B had not occurred, neither would event Ahave (van Fraassen 1980, 118). That’s because (as just noted)explanations are frequently causal in character, and analyses ofcausation typically invoke some sort of counterfactual. Anothercomponent of the constructive empiricist’s efforts at showingexplanation to be context-dependent, then, amounts to his expositionof the context dependence of counterfactuals.

Van Fraassen points out that any counterfactual has a ceteris paribusclause, but what is “being kept equal” by the asserter ofthe counterfactual varies from context to context. For example,consider the counterfactual, “If Tom were to light the fuse,there would be an explosion.” If the ceteris paribus clause ofthe speaker keeps constant the fact that the fuse leads to a barrel ofgunpowder, and the fact that lit fuses leading to barrels of gunpowdertypically result in explosions, then the counterfactual would, in thatcontext, be true. If, on the other hand, the ceteris paribus clause ofthe speaker also kept constant the fact that Tom is generally paranoidabout explosions around barrels of gunpowder and fuses, and would onlylight the fuse if he had disconnected the fuse from the barrel, thenthe counterfactual would, in that context, be false (1980, 116). Untilthe context that fixes the ceteris paribus clause is specified, wecannot say what the truth value of the counterfactual in question is.Only once the context is determined does the counterfactual admit ofan objective truth value.

One of the reasons the constructive empiricist highlights the contextdependence of explanation is that she wishes to show how efforts atexplaining various parts of the world extend beyond the activity ofscience. Since, for instance, the propositions of science are notcontext-dependent in character, but the counterfactuals involved inexplanation are, we have reason to think that explanation involvessomething more than the descriptive information science gives us:namely, the context-dependent interests of the individual seeking anexplanation in answer to some question. Also, if (as seems likely) theconcept of a law of nature has to be understood in a counterfactualway, counterfactuals’ context-dependence implies that thoselaws, too, go beyond what science reveals to us (van Fraassen 1980,118).

It should be clear here, then, that the constructiveempiricist’s efforts at showing explanatory efforts to extendbeyond the activity of science are part of an effort to show that thescientific realist is mistaken in thinking that science gives usreason to think that claims about causation, laws of nature, and othercounterfactuals represent objective, context-independent truths aboutthe world.

Scientific realists might point out that constructive empiricists doallow that explanatory power can count as a pragmatic virtue of atheory (van Fraassen 1980, 89). But, one might naturally think, noscientist can acknowledge the explanatory power of a theory withouttaking the theory to be true. So, continues the scientific realist,the constructive empiricist cannot admit the usefulness of explanatorypower to the scientist without also regarding the scientist as takingher theories to be true.

The constructive empiricist disagrees. Among other reasons, she cancite the earlier mentioned explanatory power of false theories.Additionally, the constructive empiricist might insist that use of atheory need not entail a commitment to the theory’s entireontology. A person offering an explanation speaks from within thelanguage of the theory she accepts. Consistent with that acceptance,she is “conceptually immersed” within the theory. But suchuse of language need not reflect the individual’s epistemiccommitment, which may be merely to take the theory to be empiricallyadequate (van Fraassen 1980, 151–152). So, for instance, talk ofpossibility and necessity can be thought of not as talk about someobjective modality in nature, but as talk of what phenomena fit in themodels of the accepted theory (van Fraassen 1980, 201–202).‘X is possible’ can be interpreted as‘X appears in some model of the theory,’ while‘X is necessary’ can be read as ‘Xappears in every model of the theory.’ Again, the constructiveempiricist sees the scientist as “immersing” herself inthe world of the theory, talking as if the theory were true, withlanguage reflecting the structure of the theory. But she need not takethe theory’s modal structure to correspond to any inreality.

2.6 Avoiding Inflationary Metaphysics

We can see in the above discussion of the pragmatics of explanationwhy the constructive empiricist thinks constructive empiricism canhelp us to make sense of science “without inflationarymetaphysics” (van Fraassen 1980, 73). By “inflationarymetaphysics,” van Fraassen has in mind the scientificrealists’ typical beliefs in, for example, laws of nature,natural kinds, and objective modality.

The constructive empiricist recognizes that believing in empiricaladequacy involves sticking our necks out, just as believing in truthdoes; nonetheless,

… there is a difference: the assertion of empirical adequacy isa great deal weaker than the assertion of truth, and the restraint toacceptance delivers us from metaphysics. (van Fraassen 1980, 69)

Scientific realists might not be moved by this consideration, becausethey might not see any problem with inflationary metaphysics. Thepoint ofThe Scientific Image, according to van Fraassen, wasto answer the question: what should an empiricist think about science?Since an empiricist would want to avoid inflationary metaphysics, thisconsideration would move them to favor constructive empiricism. Thequestion of why one would want to be an empiricist is taken up in vanFraassen’s 2002 book,The Empirical Stance.

3. Arguments Against Constructive Empiricism

3.1 The Miracle Argument

One way that the constructive empiricist might indirectly supportconstructive empiricism is by taking issue with Hilary Putnam’smiracle argument for scientific realism. This argument holds thatscientific realism “is the only philosophy that doesn’tmake the success of science a miracle” (Putnam 1975, 73). Putnamgoes on to argue that the statements that a scientific realist wouldmake about our mature scientific theories are “part of the onlyscientific explanation of the success of science.” To give anadequate scientific description of science, scientific realism needsto be assumed.

Putnam’s basic idea is as follows: if the scientific theoriesare false, why would they be so successful? Van Fraassen famouslyreplies with an evolutionary analogy:

I claim that the success of current scientific theories is no miracle.It is not even surprising to the scientific (Darwinist) mind. For anyscientific theory is born into a life of fierce competition, a junglered in tooth and claw. Only the successful theories survive—theones whichin fact latched on to actual regularities innature. (van Fraassen 1980, 40)

Van Fraassen’s point is that a theory can be empiricallyadequate, and hence latch on to the observable regularities in nature,without being true. The scientific competition between theories hingeson which theory accurately describes the observable world; it does nothinge on which theory is actually true. Thus, it would not bemiraculous for science to arrive at an empirically adequate,scientifically successful, yet false theory. (See the discussion ofthe Miracle Argument in the entry onscientific realism for more on the miracle argument as a consideration in favor ofscientific realism.)

3.2 Inference to the Best Explanation

Inference to the Best Explanation is the controversial rule ofinference which basically holds that, out of the class of potentialexplanations we have of some phenomena, we should infer that the bestexplanation is the true one. If Inference to the Best Explanation is arule we do (or ought) to follow, then it looks as if scientificrealism is an accurate description (or prescription) of the aims ofscience—we should acknowledge the reality of the entities ourbest explanatory theories postulate, even if those entities areunobservable.

The constructive empiricist might offer several responses to thischallenge:

Inference to the Best Explanation doesn’t automatically winas a description of scientists’ actual inferential practice,since that practice may be equally well described by saying thatscientists believe our best explanatory theories to be empiricallyadequate (rather than true) (van Fraassen 1980, 20–21). Note,though, that the constructive empiricist does not actually endorse therule that we should believe that the best explanation is empiricallyadequate (contrary to how van Fraassen, for instance, has sometimesbeen read; see, e.g., Bandyopadhyay 1997).
The scientific realist thinks that theories can only adequatelyexplain regularities in nature if we take the theories to be true. Buttheories can explain if we merely take the theories to be empiricallyadequate. So even if we allow Inference to the Best Explanation as alegitimate rule of inference, the realist has to offer some additionalreason to think “T is true” is a better explanation than“T is empirically adequate” (van Fraassen 1980, 21).
It may be that all the potential explanations we have are bad, andhence we would be unwise to believe that one of those explanations isthe true one (van Fraassen 1989, 143–145). It’s plausibleto think any argument is mistaken that suggests that we are privilegedto hit on the right range of potential explanations to beginwith.
Any probabilistic formulation of Inference to the Best Explanationis probabilistically incoherent. A Bayesian will coherently update inlight of new evidence, but then the proponent of Inference to the BestExplanation wants the Bayesian to unwarrantedly give extraprobabilistic weight to the hypothesis that is the best explanation(van Fraassen 1989, 160–70).

In sum, because the constructive empiricist rejects Inference to theBest Explanation, she is not moved by arguments for scientific realismthat make use of that rule of inference. (See the discussion ofskepticism about inference to the best explanation in the entry onscientific realism for an elaboration of doubts about the use of inference to the bestexplanation as a motivating consideration in favor of scientificrealism.)

3.3 The Observable/Unobservable Distinction

A standard type of objection to constructive empiricism, one that wasespecially prevalent soon afterThe Scientific Image waspublished, is the type of objection that takes issue with the clarityor cogency of the observable/unobservable distinction. A few examplesof this type of objection will be presented in this section, alongwith constructive empiricist replies.

By the constructive empiricist’s lights, distant macroscopicobjects are observable, since if we were nearby we could see them.Paul Churchland (1985, 39–40) takes issue with the importancethe constructive empiricist attaches to size, as opposed tospatiotemporal proximity. Churchland points out that it is just acontingent fact that humans have control over their spatiotemporallocation, but not over their size. Churchland concludes that thedistinction between things that are unobserved but observable, andthings that are unobservable, “is only very feebly principledand is wholly inadequate to bear the great weight that van Fraassenputs on it” (Churchland 1985, 40).

Van Fraassen replies with the recognition that “scientificrealists tend to feel baffled by the idea that our opinion about thelimits of perception should play a role in arriving at our epistemicattitudes toward science” (1985, 258). Constructive empiricistsare not asserting any metaphysical difference in the world on thebasis of the observable/unobservable distinction; they are just sayingthat that distinction is relevant to the epistemic attitudes we take.Since “experience is the sole legitimate source of informationabout the world” (van Fraassen 1985, 258), it makes sense thatwhat we can experience influences our epistemic attitudes. (Note thatin his 2002 bookThe Empirical Stance, van Fraassen callsinto question his 1985 statement about experience.)

A different argument by Churchland (1985, 44–45) asks what theconstructive empiricist would say about beings who are like us exceptthat they are born with electron microscopes permanently attached totheir left eyes. Churchland says that the electron-microscope-eyehumanoids would count viruses as part of their ontology, and yet bythe constructive empiricist’s lights we can’t, even thoughwe are functionally the same as the humanoids when we put our left eyeagainst the viewfinder of an electron microscope.

The constructive empiricist might reply that we are not warranted insaying that the humanoids have theexperience of virusesunless we already treat the humanoids as being part of our epistemiccommunity (van Fraassen 1985, 256–257). If we do expand ourepistemic community to include them, then the constructive empiricistis happy to say that in that situation viruses are observable. But ifwe do not accept them as part of our epistemic community, then we willsimply analyze them as like us, except having electron microscopesattached to themselves, and we will say that they are “reliableindicators of whatever the usual combination of human with electronmicroscope reliably indicates” (van Fraassen 1985, 257). In thatcase the extension of ‘observable’ is unchanged.

Another argument calling into question the significance of theobservable/unobservable distinction is presented by Ian Hacking (1985,146–147). Hacking considers a machine which makes grids of thesame shape but various sizes. We can see grids with the same overallshape of smaller and smaller size, but the machine makes some gridsthat are too small to be seen with the unaided eye. When looked atthrough a microscope, however, the unobservable grids are seen to havethe same shape as the observable ones. Hacking writes:

I know that what I see through the microscope is veridical because wemade the grid to be just that way. I know that the process ofmanufacture is reliable, because we can check the results with themicroscope. Moreover we can check the results with any kind ofmicroscope, using any of a dozen unrelated physical processes toproduce an image. Can we entertain the possibility that, all the same,this is some gigantic coincidence? (Hacking 1985, 146–147)

Hacking concludes that it would be unreasonable to be an anti-realistabout the unobservable grid, and hence we should at least sometimesbelieve what science tells us about unobservables.

Van Fraassen (1985, 298) replies by pointing out an unwarrantedsupposition in Hacking’s argument: the claim that we made thegrid to be that way implies what is under dispute, that the grid wassuccessfully made to be that way. Regarding the argument that, ifdifferent types of microscopes make similar observations, then theobservations must be veridical, van Fraassen replies that thatargument

reveals only the unstated premise that the persistent similarities inthe relevant phenomenarequire,must have, a trueexplanation. (van Fraassen 1985, 298)

But this is a premise that the constructive empiricist rejects.

Here van Fraassen is allowing for the possibility that theconstructive empiricist can reasonably be agnostic about the grid. VanFraassen replies in a similar fashion to an objection that Paul Tellerputs forth about the immediacy of objects viewed through amicroscope.

Teller (2007) claims that the images produced by many scientificinstruments require some interpretative effort for us to makeassertions about what it is that we are seeing. What we see throughoptical microscopes, on the other hand, is importantly different. Insuch an observation, we take ourselves to see the object beingmagnified itself, immediately and without interpretative effort.

The conclusion Teller draws is that contrary to what van Fraassenclaims, what is observable extends beyond what members of ourepistemic community can observe unaided by measuring instruments. Whatis observable minimally also includes the objects viewed throughoptical microscopes, as well as other objects whose observation issimilarly unmediated by interpretation (132–134).

In reply, van Fraassen (2001) suggests that what we see through amicroscope is akin to reflections seen in mirrors and other reflectivesurfaces—the reflection of a tree in a body of water, forinstance. In both the case of the observation via the microscope andthe object viewed in a reflection, we might assert that what we areseeing is a real object. But van Fraassen points out an importantdifference between the reflected object and our observation throughthe microscope. We are confident that the reflection is of a realobject because we can observe certain invariances between the objectpurportedly being observed (the tree), the reflective image, and ourvantage point. We can, for instance, see that the tree maintains acertain fixed position relative to the reflective body, and we can seethat the angle subtended by the lines between us and the two bodies isa particular function of the observer’s position. Theobservation of these invariances is possible, in part, because thetree is itself observable without the aid of instruments (van Fraassen2001, 160).

That, however, is not true of the objects—the paramecia,say—that are purportedly being observed through the microscope.Because the paramecia are not directly observable without instruments,we can only hypothesize that there are objects being observed forwhich the invariant geometric relations hold. It is possible for us,then, to maintain an agnosticism about the paramecia that wecan’t about the tree (160). We can regard our observations viathe microscope the same way we regard our observations ofrainbows—namely, as observations of phenomena that are public(even capable of being captured by photographic equipment) without atthe same time being observations of some existent object (162). (Wesay that the rainbow is not an actual physical object because it doesnot participate in the invariant geometric relations we expect ofactual physical objects: “If the rainbow were a thing, thevarious observations and photos would all locate it in the same placein space, at any given time” (157) ).

Alspector-Kelly (2004) claims that there is not the differencedescribed here between aided and unaided perception. If theconstructive empiricist insists that rainbows, reflections, and thelike constitute publicly observable phenomena despite not amounting toactually existing objects, then what we experience in the case ofunaided veridical perception is also some kind of image-likeobservable phenomena:

…when we look directly at the tree we are also postulating anappropriate relation between object, image, and vantage point, namely,between the tree itself, our perceptual experience of the tree, andthe vantage point of our bodily location. (Alspector-Kelly 2004, 336)

Insofar as it is appropriate to speak of a perceptual image whencharacterizing the view through the microscope—even when, so faras the science of microscopy informs us, that view isveridical—it is appropriate to speak of a perceptual image whencharacterizing naked-eye visualization, even when that view isveridical. (Alspector-Kelly 2004, 338)

If this is true, then unaided veridical perception is notdistinguished from aided perception in the way van Fraassen suggests.Unaided veridical perception is as much mediated by image-likeobservable phenomena as aided perception is.

As we will see in §3.7, the constructive empiricist mightnaturally express skepticism, in the case of unaided veridicalperception, about the existence of anything like image-like phenomena.Kusch (2015) points out one reason for skepticism: the phenomena inquestion exhibit fewer of the invariant relations—“unlike,say, rainbows, visual experience cannot be photographed”(177)—that would allow us to characterize the phenomena aspublic, verifiable ones capable of empirical study.

A constructive empiricist might also respond to Alspector-Kelly byadvocating something like a disjunctivist view of perception, denyingthat what is observed in the disparate cases really is the same. Onsuch a view, unaided veridical perception really is of actual physicalobjects, whereas perception with instrumentation results only in theexperience of some kind of publicly observable phenomena akin torainbows and reflections. It remains to be seen whether independentmotivation for such a view can help recommend it over the alternativeoffered by the defender of microscopic observables.

3.4 Observable versus Observed

According to the constructive empiricist, “there is no purelyepistemic warrant for going beyond our evidence” (van Fraassen2007, 343). But then why does the constructive empiricist hold thatthe aim of science involves going beyond our evidence? Empiricismwants to be epistemically modest, but belief that a theory isempirically adequate goes well beyond the deliverances of experience.Hence, one can object to constructive empiricism by suggesting that itis not sufficiently epistemically modest: the doctrine that the aim ofscience is truth about what is observable should be replaced with thedoctrine that the aim of science is truth about what’s actuallybeen observed. (For versions of this criticism, see for exampleGutting 1985, Railton 1990, Rosen 1994, and Alspector-Kelly 2001.)

The constructive empiricist’s reply, as presented by Monton andvan Fraassen (2003, 407–408), is as follows. Constructiveempiricism incorporates a prior commitment to the rationality ofscience—it is a doctrine about what the aim of science actuallyis; it is not attempting to present a revisionary account of howscience should be done. According to the doctrine that the aim ofscience is truth about what’s been observed,

there would be no scientific reason for someone to do an experimentwhich would generate a phenomenon that had never been observed before.But one of the hallmarks of good scientists is that they performexperiments pushing beyond the limits of what has been observed sofar. (Monton and van Fraassen 2003, 407)

The constructive empiricist can hence conclude that the doctrine thatthe aim of science is truth about what’s been observed“fails to capture our idea of what it is to do goodscience” (Monton and van Fraassen 2003, 407).

3.5 Empirical Adequacy of Theories as Inadequate for Capturing the Aim of Science?

Monton and van Fraassen’s reply here indicates that the reasonto prefer truth about the observable, rather than truth about theobserved, as the aim of science is the following:

we could not make sense of the practice of good science— and, inparticular, of the motivation to carry out experiments that generatenew observable phenomena— if the aim of science were merelytruth about the actually observed.

Dellsén 2024 suggests that a similar charge— aboutfailing to make sense of scientific practice— can be leveled atconstructive empiricism itself. The aspect of scientific practiceDellsén thinks constructive empiricism cannot explain is theinterest of science in expanding the realm of what counts asobservable. We might naturally think that science, indeed, has thatinterest: given the option, scientists would prefer to expand whatcounts as observable for their epistemic community, rather than toforego such an enhancement. A more discerning power of observation ispreferable to a less discerning one.

For the constructive empiricist, though, the aim of science is truthabout what is observable, where what counts as observable isdetermined by the constitution of ourcurrent epistemiccommunity, not by some future constitution for it. Dellsénargues, then, that if constructive empiricism were true, scientistswould have no incentive to pursue greater powers of observation, sincedoing so need not lead to greater success at achieving science’saim. In fact, greater powers of observation might very wellundermine the success of current theories, given the additionalphenomena that those powers might reveal: phenomena that couldconceivably render the current theories empirically inadequate. So ifconstructive empiricism were true, scientists would have adisincentive to augment their community’s powers ofobservation, contrary to what we might think guidelines for the properpractice of science would recommend (137–140).

In reply to Dellsén’s objection, the constructiveempiricist might embrace the response that van Fraassen himself givesto Dellsén in van Fraassen 2024. There (216–218), vanFraassen suggests that while science does aim at empirical adequacyfor its theories, that aim could be construed as non-exclusive:science might also pursue other aims— for instance, greaterscope / completeness in its theories.^[1] It might be in the pursuit of one of these other goals thatscientists have reason to expand the powers of observation for theirepistemic community.

Another response van Fraassen 2024 makes in reply to Dellséncalls into question the claim that pursuing the aim of empiricaladequacy for their investigated theories might disincentivizescientists from expanding their community in observability-relatedways. Van Fraassen 2024 (218–221) has us consider a communitythat does expand itself in this way, to include new members N thatclaim certain elements E of the world to be observable that are notobservable to the community’s original members O. Four cases arepossible concerning some theory T of interest to the scientists:^[2]

N’s reportscan be duplicated by O using measuringinstruments, and the N’s reportscan be accommodated byT.
N’s reportscan be duplicated by O using measuringinstruments, and N’s reports cannot be accommodated byT.
N’s reports cannot be duplicated by O using measuringinstruments, and N’s reportscan be accommodated byT.
N’s reports cannot be duplicated by O using measuringinstruments, and N’s reports cannot be accommodated byT.

Cases (1)–(3) do not provide a reason for scientists to avoidthe expansion of their epistemic community (on pain of that expansionundermining the empirical adequacy of T). First, (1) and (3)themselves would not result in T being rendered empiricallyinadequate. Secondly, even though (2) does result in T being renderedempirically inadequate, that rendering is not the result of theexpansion of the community; in that case, instrument-aidedobservations by O alone would show T to be empirically inadequate.

Only case (4), then, poses a possibility in which expansion of thecommunity threatens T’s empirical adequacy. With respect to (4),though, van Fraassen suggests that without instrument-aidedverification of M’s reports, O can reasonably choose to withholdbelief about those reports counting as legitimate observation reports(220–221). As a result, M can continue to insist that T isempirically adequate, accommodating of whatever reports are counted byM as legitimate observation reports.

In sum, then, none of the cases (1)–(4) necessarily poses athreat to the empirical adequacy of T that did not already exist,pre-expansion of the community of scientists. As a result, an interestin maintaining T’s empirical adequacy would not disincentivizethe scientists from expanding their epistemic community and therebyincreasing what counts as observable for it.

3.6 Commitments to modal realism in talk of observability?

So the constructive empiricist is firm in her construal of the aim ofscience as truth about the observable. One might worry, though, asJames Ladyman (2000) does, that such a view brings with it acommitment to modal realism and belief in whatever entities such acommitment may require. So, for instance, talk of observability mightcommit the constructive empiricist to belief in the existence ofpossible worlds, a commitment that an empiricist would prefer not tomake.

To understand why one might think this way, consider the following. Asnoted inSection 1.6 above, one natural way of understanding “x isobservable” is in the following counterfactual manner:

x is observable iff if a suitably constituted observer werein relevant circumstancesC, she would observex.

If the truth conditions of counterfactuals are understood in terms ofpossible worlds, it is easy to see how beliefs about what isobservable entail commitments to the existence of such worlds.

One reply to this threat of modal realism is that contrary to theinitial impression provided by the counterfactual characterization ofobservability, observability is not a modal property, after all(Monton and van Fraassen 2003, 411). As explained inSection 2.5 above, van Fraassen takes the truth of counterfactuals to becontext-dependent. Once a context is fixed, counterfactuals can beexpressed as non-modal conditionals. In the case of thecounterfactuals that explicate observability, then, fixing theepistemic community of the “suitably constituted observer”transforms the counterfactuals into straightforward non-modalconditionals whose truth or lack thereof we can empiricallyinvestigate (Monton and van Fraassen 2003, 413–414). Belief inthe truth of some claim of the form ’x is observable’amounts simply to belief in the truth of such a context-fixed,non-modal conditional.

Whether such conditionals are true is an empirical question to whichour best scientific theories may provide an answer. So even thoughobservability represents some objective, theory-independent propertyof the world (van Fraassen 1980, 57), we can use our best scientifictheories to answer the question, “What is observable?”(Monton and van Fraassen 2003, 415–416):

Consider the claim ‘if the moons of Jupiter were present to us(in the right kind of circumstances) then we would observethem’. The way to understand the claim is to note that, eventhough it is a counterfactual, it is entailed by facts about theworld: facts that the moons of Jupiter are constituted in a certainway, and facts that we are constituted in a certain way. These factscan be disclosed by empirical research. In practice, not all theempirical research has been done, so we have to rely on our currentbest theories to determine what these facts are.

For worries about methodological circularity in using our acceptedtheories to supply facts about observability—facts that bear onthe theories’ own empirical adequacy—seeSection 3.8 below.

One additional worry about Monton and van Fraassen’s non-modalcharacterization of observability is given by Ladyman (2004). Considerthe claim ‘x is observable’ for somexthat is never actually observed. Ladyman asserts that no empiricalinvestigation will be sufficient to establish the truth of therelevant non-modal conditional “unless we take it that thespecification by science of some regularities among the actual factsas laws … is latching onto objective features of theworld” (Ladyman 2004, 762). As Ladyman sees it, only objectivelyexisting laws, and not pragmatically selected empirical regularities,can underwrite claims about the observability of objects neveractually observed.

Paul Dicken (2007) offers another promising way for the constructiveempiricist to resist the threat of a commitment to modal realism thatis posed by talk of observability. He suggests that the constructiveempiricist take the same attitude toward the truth of observabilitycounterfactuals that she takes toward other claims of endorsedscientific theories: namely, acceptance of the counterfactuals ratherthan belief in them (608).

Indeed, given that observability is itself supposed to be a subject ofscientific theory (as noted above), acceptance is the natural attitudefor a constructive empiricist to take toward the counterfactuals thatexplicate observability. She relies on those counterfactuals in theway she relies on the other elements of the theories she accepts, even(in certain contexts) talking as if the counterfactuals are true. Inthis way, according to Dicken, she can make use of claims about whatis observable while at the same time being agnostic about possibleworlds whose existence is purportedly entailed by the truth of thecounterfactuals explicating observability.

3.7 Why Not Just Believe in Sense Data?

An objection related to the one fromSection 3.4 is the following. The constructive empiricist errs not just inbelieving claims about what is unobservable-but-not-actually-observed,but also in believing claims about actually observed entities thelikes of macroscopic physical objects. If one really takes to heartthe advice that one’s beliefs should not extend beyondone’s evidence, then one should limit belief to claims about themental experiences that one is having.

A constructive empiricist might reply to the objection as follows:

Such events as experiences, and such entities as sense-data, when theyare not already understood in the framework of observable phenomenaordinarily recognized, are theoretical entities. They are, what isworse, the theoretical entities of an armchair psychology that cannoteven rightfully claim to be scientific. I wish merely to be agnosticabout the existence of the unobservable aspects of the world describedby science—but sense-data, I am sure, do not exist. (vanFraassen 1980, 72)

3.8 The Hermeneutic Circle

As noted inSection 1.6 above, the constructive empiricist says that what counts asobservable is relative to who the observer is and what epistemiccommunity that observer is part of. Since the observer is her- orhimself the subject of scientific theory, what counts as observable isalso the subject of scientific theory. Here are two worries about theuse of scientific theory as the determiner of observability:

Relativity: If a theory of observability determineswhat is observable, and empirical adequacy is assessed in terms ofwhat is observable, then a theory of observability can name the termsof its own empirical adequacy. Empirical adequacy becomes radicallyrelative. With no objective, theory-independent constraints onempirical adequacy, it’s “anything goes” when itcomes to theory acceptance: one simply adopts the theory ofobservability that underwrites the empirical adequacy of whichevertheory one is interested in accepting.
Circularity: if scientific theory is the arbiter ofobservability, then an individual has no choice but to use the theoryof observability she accepts as a guide to observability, and hence asa guide to empirical adequacy, and hence as a guide to whether or notto accept that very theory. But to use the theory as a guide towhether or not to accept that theory involves the individual inepistemic circularity.

The constructive empiricist might reply to Relativity by insistingthat while we must look to science for an account of observability,observability is not a theory-dependent notion. What counts asobservable is an objective, theory-independent fact. So there’sno danger of relativism about empirical adequacy (van Fraassen 1980,57–58).

This response only addresses Relativity; the objectivity ofobservability does not save us from the epistemic circularity thatcomes about from our having to use a theory of observability as thestandard of empirical adequacy by which we assess that theory’sown empirical adequacy. The epistemic circularity has to do with howwe come to certain beliefs about observability, not with theobjectivity of the observability facts.

If such circularity were avoidable, then it would be good for us toavoid it. Unfortunately for us, the constructive empiricist might say,it is not avoidable (Monton and van Fraassen 2003, 415–416,maintains this line). Advocates of constructive empiricism mightinsist that any search for a Cartesian-style guarantee of thecorrectness of our theory of observability is a search in vain. Wehave to accept some such theory, imperfect though it may be, andmodify our acceptance if experience proves that acceptance to bemisplaced.

3.9 Observability of the Microscopic

The Hermeneutic Circle objection was prefaced on the claim that whatcounts as observable is, according to the constructive empiricist,determined by scientific theory. Another worry based on thatpresupposition, raised by Alspector-Kelly (2004), is that scientifictheory determines much more to be observable than the constructiveempiricist typically allows. On Alspector-Kelly’s view, weshould countenance as observable whatever science says we can havereliable information about on the basis of perceptual experience, andscience says we can have reliable information about what isperceptually revealed to us via microscopes.

The electron microscope is a window on the microcosm because itgenerates reliable images… We know of that reliability invirtue of knowing the science behind it, just as the constructiveempiricist knows the limits of unaided human observation by knowingthe science behind the perceptual process. (Alspector-Kelly 2004, 347)

Given what it is for experience to provide us with information aboutthe world, electron microscopes and the rest do precisely that for ourcommunity… even a relatively conservative estimation of ourperceptual abilities, concerned with both reliability and fidelity,has them extending much farther into the microcosm than the overlyconservative constructive empiricist is willing to recognize.(Alspector-Kelly 2004, 348)

In response to Alspector-Kelly, Kusch (2015) insists that theconstructive empiricist can rely on science to determine what countsas observable,without at the same time countenancing themicroscopic as observable. That’s because “the phenomenonof naked-eye observation calls for one (kind of) theory; thephenomenon of instrumentally-aided eye-use calls for at least two(kinds of) theories: the theory covering naked-eye observation andtheories of the instrument and its interaction with our nakedeyes” (179). As noted earlier, constructive empiricists valueepistemic modesty. If a constructive empiricist can rely on science togive us an account of the kind of unaided observation in which allscience is grounded, without at the same time having to make use ofscientific theories that go farther afield, then by the constructiveempiricist’s lights, that more modest invocation of science isto be preferred in deciding the question of observability.

3.10 Commitment to the Existence of Abstract Objects?

Rosen (1994, 164–169) contends that a scientist cannot remainfaithful both to the epistemic standards of the empiricist at the sametime that she accepts various scientific theories in the way that theconstructive empiricist describes. If what Rosen says is correct, thenconstructive empiricism fails as an explanation of how a committedempiricist can endorse the activity of science as rational.

Rosen’s argument goes as follows. Using the terminology of vanFraassen’s semantic view of theories (described in Sec. 1.5above), Rosen says an individual believing a theory to be empiricallyadequate

is thereby committed to at least three sorts of abstract objects:models of the phenomena (data structures), the models that compriseT, and functions from the one to the other. To suspendjudgment on the existence of abstract objects is therefore to suspendjudgment on whether any theory is empirically adequate, and this just[is] to give up acceptance altogether. (166)

Indeed, we would naturally suspect that a constructive empiricistwould suspend belief about the existence of abstract objects,which are unobservable entities if anything is. So it looks as if anempiricist cannot accept any scientific theories, if acceptanceamounts to what the constructive empiricist says it does.

One possible response the constructive empiricist might give here is afictionalist account of mathematical objects. Embracing such afictionalist view, an individual could use the theoretical apparatusof mathematics without committing herself to the existence of theobjects that are the alleged subject matter of mathematical theories.Rosen (1994) considers this response but contends that it is not onethat a constructive empiricist may want to accept. The problem, Rosensays, is that to embrace fictionalism about a theoryT thatone accepts commits one to believing claims of the following form:

(T ′) the world is such that if there were sucha thing asT, it would be empirically adequate (167).

Such a counterfactual-involving belief appears to commit the believerto the truth of certain modal facts, a commitment eschewed by thetypical Hume-inspired empiricist. Perhaps the constructive empiricistcan view the relevant counterfactuals as reducible to non-modalconditionals, in the spirit of the context-dependent reduction ofcounterfactuals to non-modal conditionals entertained inSection 3.6 above. If such a reduction can be successfully undertaken, theconstructive empiricist can avoid commitment to belief in the truth ofthe relevant modal facts.

Whether the constructive empiricist would ultimately want to endorsesome fictionalist view about mathematical objects is an open question.For an attempt at developing a constructive empiricist philosophy ofmathematics, see Bueno 1999.

3.11 Resistance to characterizing science in terms of aims

Rowbottom (2019) contends that it would be wrong to characterize thedisagreement between the constructive empiricist and the scientificrealist as a debate about the aims of science. In extending hiscritique, we might also be persuaded that constructive empiricism ismistaken in thinking that any philosophy of science ought centrally tobe about aims at all. In characterizing what science is, we shouldinstead focus on the many disparate activities and products of scienceitself, independent of any general aim or “point” to theactivity. As Rowbottom says,

One can learn how to perform various scientific tasks, and performthem well, without any explicit or implicit reference to an ultimateor central ‘point’ of the exercise—the overarchingprocess—of which they are a part. One may focus instead on theimmediate products of these tasks… ‘What isscience?’ can be answered by pointing to those processes, howthey interact, and so forth. And what science can achieve may be(largely or wholly) independent of what its practitioners think it canachieve, or any rather mystical ‘point’ of the exercise(454–455).

A defender of constructive empiricism might suggest that unless wethink of the activity of science in relation to some aim or other, wecannot properly understand that activity; and unless we understand asunited under some general aim all the disparate many ways that scienceis undertaken, we cannot understand those many practices as partsof science (as opposed to, say, parts of religion or politicsor …). The activity is rendered intelligible only in light ofthe point and purpose of undertaking it, and it is renderedintelligibleas science only in light of a point or purposeshared with other activities regarded as scientific.

As van Fraassen (1994) puts it,

[S]cientists with their very different motives and convictionsparticipate in a common enterprise, defined by its own internalcriteria of success, and this success is their common aim‘inside’ this cluster of diverging personal aim [sic]. Howelse could they be said to be collaborating in a common enterprise?The question is only what that defining criterion of success is(182).

Still, even if we can offer an interpretation of science and itsactivity as animated by a particular aim, which aim that is may beless important in characterizing science than the activity itself.Rowbottom presses this point with the following thoughtexperiment:

Imagine members of an alien species, for whom acceptance—or ifyou prefer to reserve ‘acceptance’ for humans, call it‘a-acceptance’—involves belief neither in(approximate) truth nor empirical adequacy. (This might be due topsychological constraints. A-acceptance could instead involve beliefin significant truth content, high problem-solving power, approximateempirical adequacy, and so on.) Would we want to say that they wereincapable of doing science? Or failing that, would we want to insistthat they couldn’t do anything with the ‘character’of science? That would be strange. For they could have institutionssimilar to our universities, and have theories similar to ourscientific theories, arrived at by the use of similar procedures. Theycould also use these theories for exactly the same purposes for whichwe use our scientific theories: to explain the origins of theuniverse, to build spacecraft, and so forth (456).

Rowbottom here is, of course, describing theory acceptance. Insofar,though, as a theory’s acceptability is determined by the degreeof the theory’s success at achieving a particular aim or aims,we can take the point to be equally about aims. We can understand,that is, the aliens as engaging in science even if they are not aimingfor empirically adequate, or true, theories. In comparison to theactivity itself, aims appear to be the less important thing to focuson in characterizing the activity as distinctively scientific.

How might a constructive empiricist reply? As noted in §1.4above, constructive empiricism is to be regarded as the bestinterpretative account of the activity of science that renders itconsistent with the empiricist’s own standards of rationalactivity. It is, as van Fraassen (1994) says, what allow us to“make sense of those activities which we all agree arepart of science” (190). As such, it is not beholden toscientists’ own professed aims in the activity the scientistsundertake. Even if scientists—alien or human—regardthemselves as being principally concerned with truth, orproblem-solving, or predictive utility, none of those aims could beachieved without science being at least minimally aimed at empiricaladequacy for its theories. Positing empirical adequacy as the aim ofscience, then, allows the constructive empiricist to best and mostmodestly make sense of the activity of science. The variability ofparticular scientists’ individual or collective aims does notundercut the singular and important role empirical adequacy plays inhow we might philosophically best interpret science and its manydisparate activities.

Bibliography

Alspector-Kelly, M., 2001, “Should the Empiricist be aConstructive Empiricist?”,Philosophy of Science,68(4): 413–431.
–––, 2004, “Seeing the Unobservable: VanFraassen and the Limits of Experience”,Synthese, 140:331–353.
Bandyopadhyay, P., 1997, “On an Inconsistency inConstructive Empiricism”,Philosophy of Science, 64(3):511–514.
Beebe, J., and F. Dellsén, 2020, “Scientific Realismin the Wild: An Empirical Study of Seven Sciences and History andPhilosophy of Science”,Philosophy of Science, 87(April): 336–364.
Beisbart, C., and M. Frauchiger (eds.), 2024,ScientiﬁcTheories and Philosophical Stances: Themes from van Fraassen,Berlin/Boston: Walter de Gruyter GmbH.
Bueno, O., 1999, “Empiricism, Conservativeness, andQuasi-Truth”,Philosophy of Science, 66:S474–S485.
Churchland, P., 1985, “The Ontological Status ofObservables: In Praise of the Superempirical Virtues”, inChurchland and Hooker 1985, pp. 35–47.
Churchland, P., and C. Hooker (eds.), 1985,Images of Science:Essays on Realism and Empiricism (with a reply from Bas C. vanFraassen), Chicago: University of Chicago Press.
Dellsén, F., 2024, “Expanding the Empirical Realm:Constructive Empiricism and Augmented Observation”, in ClausBeisbart and Michael Frauchiger, (eds.),Scientiﬁc Theoriesand Philosophical Stances: Themes from van Fraassen , pp.127–146.
Dicken, P., 2007, “Constructive Empiricism and theMetaphysics of Modality”,British Journal for the Philosophyof Science, 58: 605–612.
Friedman, M., 1982, Review ofThe Scientific Image,Journal of Philosophy, 79: 274–283.
Gutting, G., 1985, “Scientific Realism versus ConstructiveEmpiricism: A Dialogue”, in Churchland and Hooker 1985, pp.118–131.
Hacking, I., 1985, “Do We See Through a Microscope?”,in Churchland and Hooker 1985, pp. 132–152.
Healey, R., 2019, “The Aims of Reliable Knowledge: A Replyto Seungbae Park”,Social Epistemology Review and ReplyCollective, 8 (9): 25–30 [Healey 2019 available online].
Ivanova, M., 2024, “Aesthetic Virtues and TheoryAcceptance”, in Claus Beisbart and Michael Frauchiger, (eds.),Scientiﬁc Theories and Philosophical Stances: Themes fromvan Fraassen, pp. 147–163.
Kitcher, P., and W. Salmon, 1987, “Van Fraassen onExplanation”,Journal of Philosophy, 84(6):315–330.
Kusch, M., 2015, “Microscopes and the Theory-Ladenness ofExperience in Bas van Fraassen’s Recent Work”,Journalfor General Philosophy of Science, 46: 167–182.
Ladyman, J., 2000, “What’s Really Wrong WithConstructive Empiricism? Van Fraassen and the Metaphysics ofModality”,British Journal for the Philosophy ofScience, 51: 837–856.
–––, 2004, “Constructive Empiricism andModal Metaphysics: A Reply to Monton and van Fraassen”,British Journal for the Philosophy of Science, 55:755–765.
Lombrozo, T., 2007, “Simplicity and probability in causalexplanation”,Cognitive Psychology, 55:232–257.
Monton, B. (ed.), 2007,Images of Empiricism: Essays onScience and Stances, with a Reply from Bas C. van Fraassen,Oxford: Oxford University Press.
Monton, B., and B. van Fraassen, 2003, “ConstructiveEmpiricism and Modal Nominalism”,British Journal for thePhilosophy of Science, 54: 405–422.
Railton, P., 1989, “Explanation and MetaphysicalControversy”, in P. Kitcher and W. Salmon (eds.),ScientificExplanation, Minneapolis: University of Minnesota Press, pp.220–252.
Rochefort-Maranda, G., 2011, “Constructive Empiricism andthe Closure Problem”,Erkenntnis, 75: 61–65.
Rosen, G., 1994, “What is Constructive Empiricism?”,Philosophical Studies, 74(2): 143–178.
Rowbottom, D., 2019, “Scientific realism: what it is, thecontemporary debate, and new directions”,Synthese,196: 451–484.
Teller, P., 2001, “Whither Constructive Empiricism?”Philosophical Studies, 106: 123–150.
Van Dyck, M., 2007, “Constructive Empiricism and theArgument from Underdetermination”, in Monton 2007, pp.11–31.
van Fraassen, B., 1980,The Scientific Image, Oxford:Oxford University Press.
–––, 1985, “Empiricism in the Philosophyof Science”, in Churchland and Hooker 1985, pp.245–308.
–––, 1989,Laws and Symmetry, Oxford:Oxford University Press.
–––, 1994, “Gideon Rosen on ConstructiveEmpiricism”,Philosophical Studies, 74(2):179–192.
–––, 1998, “The Agnostic SubtlyProbabilified”,Analysis, 58(3): 212–220.
–––, 2002,The Empirical Stance, NewHaven: Yale University Press.
–––, 2001, “Constructive EmpiricismNow”Philosophical Studies, 106: 151–170.
–––, 2007, “From a View of Science to aNew Empiricism”, in Monton 2007, pp. 337–383.
–––, 2024, “Reply to the ConferenceParticipants”, in Claus Beisbart and Michael Frauchiger, (eds.),Scientiﬁc Theories and Philosophical Stances: Themes fromvan Fraassen, pp. 207–232.

Academic Tools

How to cite this entry.
Preview the PDF version of this entry at theFriends of the SEP Society.
Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO).
Enhanced bibliography for this entryatPhilPapers, with links to its database.

Other Internet Resources

[Please contact the author with suggestions.]

Acknowledgments

Beginning with the 2021 update, Chad Mohler has taken overresponsibility for updating and maintaining this entry.

Open access to the SEP is made possible by a world-wide funding initiative.
The Encyclopedia Now Needs Your Support
Please Read How You Can Help Keep the Encyclopedia Free

Browse

About

Support SEP

Mirror Sites

View this site from another server:

USA (Main Site)Philosophy, Stanford University

Info about mirror sites

Library of Congress Catalog Data: ISSN 1095-5054

Movatterモバイル変換