G.E. Moore (1873-1958) (who hated his first names, ‘GeorgeEdward’ and never used them — his wife called him‘Bill’) was an important British philosopher of the firsthalf of the twentieth century. He was one of the trinity ofphilosophers at Trinity College Cambridge (the others were BertrandRussell and Ludwig Wittgenstein) who made Cambridge one of centres ofwhat we now call ‘analytical philosophy’. But his workembraced themes and concerns that reach well beyond any singlephilosophical programme.

• 1. Life and Career
• 2. The Refutation of Idealism
• 3.Principia Ethica
• 4. Philosophical Analysis
• 5. Perception and Sense-data
• 6. Common Sense and Certainty
• 7. Moore's Legacy
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. Life and Career

Moore grew up in South London (his eldest brother was the poet T.Sturge Moore who worked as an illustrator with W. B. Yeats). In 1892 hewent to Trinity College Cambridge to study Classics. He soon made theacquaintance there of Bertrand Russell who was two years ahead of himand of J. M. E. McTaggart who was then a charismatic young PhilosophyFellow of Trinity College. Under their encouragement Moore decided toadd the study of Philosophy to his study of Classics, and he graduatedin 1896 with a First Class degree in the subject. At this point heturned his energies towards attempting to follow in the footsteps ofMcTaggart and Russell by winning a ‘Prize’ Fellowship atTrinity College which would enable him to continue the study ofphilosophy there. In 1898 he was successful and over the next six yearshe matured as a dynamic young philosopher, actually leading Russellaway from the idealist philosophy of McTaggart and others which wasthen dominant in Britain.

Moore's Fellowship ended in 1904; after a spell away from Cambridge,Moore returned there in 1911 to a lectureship in the University and hethen lived there for the rest of his life (apart from an extended visitto the U.S.A. in 1940-44). In 1921 he became editor ofMind,the leading British philosophical journal, and in 1925 he became aProfessor at Cambridge. These two appointments confirmed his positionas the most highly respected British philosopher of the time, and withWittgenstein back in Cambridge after 1929, Cambridge became the mostimportant centre of philosophy in the world. Moore retired as Professorin 1939 (to be succeeded by Wittgenstein) and as editor ofMind in 1944; these retirements marked not only the end of hispre-eminence, but also of the golden age of Cambridge philosophy.

Early in his time in Cambridge Moore became friends with some of theyoung men who went on to form the ‘Bloomsbury Group’, suchas Lytton Strachey, Leonard Woolf and Maynard Keynes. Through thesefriendships Moore exerted an indirect influence on Britishtwentieth-century culture as profound as that of any more‘engaged’ philosopher. These long-lasting friendships bearwitness to Moore's Socratic personality and thus to a side of hischaracter which his writings do not convey. Gilbert Ryle, the Oxfordphilosopher who was Moore's successor both as editor ofMindand as the dominant British philosopher after 1945, emphasized thisside of Moore's personality:

He gave us courage not by making concessions, but by makingno concessions to our youth or our shyness. He treated us as corrigibleand therefore as responsible thinkers. He would explode at our mistakesand muddles with just that genial ferocity with which he would explodeat the mistakes and muddles of philosophical high-ups, and with justthe genial ferocity with which he would explode at mistakes and muddlesof his own. (Ryle 270)

2. The Refutation of Idealism

Moore was first drawn to philosophy through contact with McTaggartand under McTaggart's influence he fell briefly under the spell ofBritish idealism, especially the work of F. H. Bradley. Thus when in1897 he made his first attempt to win a Prize Fellowship at Trinity hesubmitted a dissertation on ‘The Metaphysical Basis ofEthics’ in which he acknowledges his indebtedness to Bradley andpresents an idealist ethical theory. One element of this theory is whathe calls ‘the fallacy involved in all empirical definitions ofthe good’, which is immediately recognisable as a precursor ofhis famous claim inPrincipia Ethica that there is a fallacy,the ‘naturalistic fallacy’, in all naturalistic definitionsof goodness. This point indicates that although, as we shall see below,Moore quickly came to reject the idealist philosophy of Bradley andMcTaggart, he held that their criticisms of empiricism, as representedby J. S. Mill's philosophy, were sound and he carried this hostility toempiricism forward into his mature philosophy. In this respect,therefore, his early idealist enthusiasm had an enduring impact on histhought.

A substantial part of this early dissertation is devoted to acritical discussion of Kant's moral philosophy, and it is striking thatalthough in his general approach and conclusions Moore endorses thekind of idealism advanced by Bradley, he is already critical of Kant'sconception of practical reason. He argues that Kant's use of thisconception blurs the distinction between ‘the psychologicalfaculty of making judgments and inferences’ and that which is‘true and objective’. This distinction, Moore maintains,‘cannot be either done away or bridged over’. Hence, heargues, Kant's conception of morality as founded ona prioriprinciples of practical reason is untenable. It is easy to see how thisline of thought could be extended to a general criticism of Kant'sconception of thea priori; and it is precisely thisgeneralisation that Moore undertakes in his successful 1898dissertation. At the same time he comes to see that his previousenthusiasm for Bradley's idealism was not well founded (though it stilltakes him a little time to accept that the arguments of Bradley andMcTaggart against the reality of time are flawed). So it is in this1898 dissertation that Moore turns decisively against idealistphilosophy, both in its Kantian and Bradleian forms.

There are several aspects to this. As I have indicated, he rejectsKant's conception of thea priori as a muddled form ofsubjectivism or psychologism. The following passage fromPrincipiaEthica (1903) is indicative of his polemic which can be found inmany of his writings of this period:

That ‘to be true’means  to bethought in a certain way is, therefore, certainly false. Yet thisassertion plays the most central part in Kant's ‘CopernicalRevolution’ of philosophy, and renders worthless the whole massof modern literature, to which that revolution has given rise, andwhich is called Epistemology. (Principia Ethica183)

The distinction Moore is drawing on here between thought on the onehand and what is objective or real on the other is one that runsthrough his critique of idealism. An important early context in whichhe elaborates it is his discussion of meaning in his famous paper‘The Nature of Judgement’ (1899), which comes largely fromhis 1898 Dissertation. Moore begins here by attributing to Bradley aquasi-empiricist view of meaning as abstracted from the total contentof judgement. This is a mistake, but what is important is what follows:as against this view Moore holds that meanings, which he calls‘concepts’, are entirely non-psychological. They cometogether in propositions, which are the ‘objects’ ofthoughts and, as such, are to be sharply distinguished from any mentalcontents or representations. Indeed true propositions do not representor correspond to a fact or real state of affairs; instead they just arefacts. He put this point very clearly in a short entry written a yearlater on ‘Truth’:

it seems plain that a truth differs in no respect from thereality to which it was supposed merely to correspond: e.g. the truththat I exist differs in no respect from the corresponding reality— my existence. So far, indeed, from truth being defined byreference to reality, reality can only be defined by reference totruth. (‘Truth’ 21)

As Moore came to see ten years later, this radical metaphysics oftrue propositions is too simple. But in the present context what isstriking about it is the way in which by itself it hovers betweenidealism and realism. If propositions are thought of as contents ofjudgment, then to hold that reality just comprises true propositions isto take an idealist stance. What makes the position realist in Moore'shands is his uncompromising realism concerning propositions andconcepts: although they are possible objects of thought, Moore writes,‘that is no definition of them’; for ‘it isindifferent to their nature whether anybody thinks them or not’(‘The Nature of Judgment’ 4)

Moore's most famous criticisms of idealism are contained in hispaper ‘The Refutation of Idealism’ (1903). The basic themeof this paper is the extension to sense-experience of the strongdistinction between the mind and its objects which we have encounteredin connection with meaning. Moore concentrates here on the case of a‘sensation of blue’ and maintains that this experience is akind of ‘diaphanous’ consciousness or awareness of blue,which is not a ‘content’ of experience at all, butsomething real whose existence is not dependent on experience. Hisargument here is in part phenomenological: ‘when we try tointrospect the sensation of blue, all we can see is the blue’(41); but he also argues that to suppose otherwise, that the‘blue’ is merely a content of the experience is to supposethat it is a quality of the experience, so that the experience is bluein much the way in which a blue bead is blue, which he takes to beabsurd. Not surprisingly Moore's critics were not happy with thiscomparison, but it was not until the formulation of the‘adverbial’ theory of experience by Ducasse in the 1940's,according to which someone who has a sensation of blue is someone who‘senses bluely’, that there was a reasonably robustresponse to Moore's criticism. What is, nonetheless, odd about Moore'spaper is that he makes no attempt to address the famous ‘argumentfrom illusion’. Moore concludes that ‘“blue” isas much an object, and as little a mere content, of my experience, whenI experience it, as the most exalted and independent real thing ofwhich I am ever aware’ (42). As he was soon to realise, moreneeds to be said to handle cases in which something which is not infact blue looks blue.

The final aspect of Moore's critical response to idealism concernshis rejection of the monism which was characteristic of Britishidealism. This is the holistic thesis that ordinary things areessentially inter-related in such an intimate way that they constitutetogether an ‘organic unity’ which is, in a sense, the onlything that ‘really’ exists, since it is the only thingwhose existence is not dependent on the existence of anything else.This thesis is especially characteristic of Bradley's idealism,according to which the Absolute is the one real thing. In his earlywritings and inPrincipia Ethica Moore engages in a good dealof polemical criticism of this thesis, but it is hard to find anyarguments against it, as opposed to a robust affirmation of a realistpluralism. Rather later, however, in his paper ‘External andInternal Relations’ (written in 1919) Moore focused on theidealist conception of internal relations which lies at the heart ofthe monist thesis. Moore's argument against the thesis that allrelations are internal starts from the claim that the burden of prooflies on its supporters since it conflicts with our common senseconviction that things are not essentially inter-related in such a waythat a change to one thing in one respect necessitates changes toeverything else. Moore then argues that the best reason one could havefor the thesis involves a logical fallacy; he shows how the thesis thatall relations are internal might be plausibly, but fallaciously,inferred from Leibniz’ Law, the uncontentious principle that thingswhich differ in their relations must differ in their identity.Simplifying a bit, and using Moore's concept of entailment (see below),his argument runs as follows:

1. Leibniz’ Law states that

   xRy entails (z = x →zRy),

   where ‘→’ is the truth-functional conditional

2. Since entailment is a necessary connection, one might infer

   xRy → Necessarily (z = x →zRy)

3. From (2) one can immediately infer

   xRy → Necessarily (x = x →xRy)

4. Sincex = x is itself a necessary truth, one can now infer

   xRy → Necessarily (xRy)

   which expresses the thesis that all relations are internal.

So, on the face of it, this thesis has here been inferred fromLeibniz’ Law. Moore observes, however, that the step from (1) to (2) isinvalid; it confuses the necessity of a connection with the necessityof the consequent. In ordinary language this distinction is not clearlymarked, although it is easy to draw it with a suitable formallanguage.

Moore's argument here is a sophisticated piece of informal modallogic; but whether it really gets to the heart of the motivation forBradley's Absolute idealism can be doubted. My own view is thatBradley's dialectic rests on a different thesis about the inadequacy ofthought as a representation of reality, and thus that one has to digrather deeper into Bradley's idealist metaphysics both to extract thegrounds for his monism and to exhibit what is wrong with it.

3.Principia Ethica

The main achievement of Moore's early period is his bookPrincipia Ethica. It was published in 1903 but was theculmination of the reflections which Moore commenced in his 1897dissertation on ‘The Metaphysical basis of Ethics’. Themain impetus, however, came from a series of lectures in London on‘The Elements of Ethics’ which Moore gave late in 1898.Moore had the text of these lectures typed up with a view to publishingthem; but as his thoughts progressed he reworked his text andPrincipia Ethica is the result of this reworking (the lectureshave recently been published asThe Elements of Ethics). Mostof the first three chapters come from the 1898 lectures; whereas thelast three chapters are largely new material.

In the first three chapters Moore sets out his criticisms of‘ethical naturalism’. At the core of these criticisms isthe thesis that the position involves a fallacy, the‘naturalistic fallacy’, of supposing that goodness, whichMoore takes to be the fundamental ethical value, can be defined innaturalistic terms, in terms, say, of pleasure or desire or the courseof evolution. As against all such claims Moore insists that goodness isindefinable, or unanalysable, and thus that ethics is an autonomousscience, irreducible to natural science or, indeed, to metaphysics.Moore's main argument against the possibility of any such definition ofgoodness is that when we confront a putative definition, such as thatto be good is to be something which we desire to desire, we can tellthat this is not a claim that is true by definition because its truthremains for us an ‘open question’ in the sense that itremains sensible to doubt it in a way which would not be possible if itwere just a definition which makes explicit our understanding of thewords. The merits of this argument are questionable; in many cases wecan sensibly doubt the truth of a definition, especially where thedefinition makes use of discoveries that have not been part of ourordinary understanding, as is normally the case with definitions in thenatural sciences. But there is, I think, a way of modifying Moore'sargument which takes it around this objection, namely by taking it torest on the epistemological thesis that ethical questions cannot beanswered without the explicit involvement of ethical beliefs. Thereason that this thesis is inimical to naturalistic definitions ofethical values is that an important role of definitions in the naturalsciences and elsewhere is that they enable one to answer questions innew ways that would not otherwise be possible: it is thanks to thedefinition of water as H₂O, and not in terms of its familiarphenotype, that we can be confident that some comets are mainlycomposed of water. But there is no way in which we would accept thatthe answer to a novel ethical question, for example concerning theacceptability of the use of human embryos for stem cell research, is tobe found by finding a definition of ethical values which enables us toanswer this question without drawing on beliefs that are expressed withthe familiar ethical ‘phenotype’, i.e., explicitly ethicalconcepts.

This defence of Moore's argument does not address a differentconcern, namely that the argument applies only to versions of ethicalnaturalism which involve a definition of ethical value, and thus thatnaturalist positions which maintain that ethical value is anirreducible natural property are not touched by the argument. Moore'sargument against positions of this kind rests on the claim that theethical value of a situation is not a feature of it which isindependent of its other properties; on the contrary it depends on itsother properties. As he puts it in the preface he composed for thesecond edition ofPrincipia Ethica, but never actuallypublished, a thing's ‘intrinsic value’ depends on its‘intrinsic nature’, and he glosses this dependence in termsof the relationship which we now call ‘supervenience’(though Moore does not use the term): things with the same intrinsicnature, or natural properties, must have the same intrinsic value (see‘The Conception of Intrinsic Value’ 286). Moore took itthat supervenience was not an inherently reductive relationship, andthus that it was consistent for him to hold that goodness is not anatural property even though it supervenes upon natural properties;but, he assumed, if one takes the view that goodness is itself anatural property, the fact that it supervenes upon other naturalproperties makes it impossible to avoid a reductive thesis. So thesupervenience of intrinsic value removes the option of a non-reductivenaturalism without contradicting his version of ethicalnon-naturalism.

Subsequent discussion has shown that the relationship betweensupervenience and reduction is a complicated matter, and though I thinkthat Moore's position is defensible this is not the place to take theissue further. Instead I want to turn to the concept of intrinsic valuewhich is central to Moore's theory. One aspect of this is easy, namelythe distinction between the ‘intrinsic’ value of asituation and its ‘instrumental’ value: this is thedistinction between the value inherent in a situation and that whichdepends only on the situation's consequences. Despite this distinctionit remains the case that intrinsic value is the fundamental type ofethical value, since instrumental value is definable in terms of theintrinsic value of a situation's consequences. But intrinsic value isnot merely non-instrumental value; for it is also to be distinguishedfrom what Moore calls the ‘value as a part’ of a situation,namely the extra contribution which the situation makes to the value ofa complex situation of which it is a ‘part’, over and aboveits intrinsic value. This is not a conception which is familiar to us,but Moore illustrates the point by the following case: althoughknowledge has little intrinsic value, the value of the aestheticappreciation of a beautiful work of art (which is, according to Moore,potentially one of the most valuable things there is) is greatlyenhanced by knowledge about it. So this kind of knowledge can have asubstantial ‘value as a part’ even though it has littleintrinsic value. As before intrinsic value remains the fundamentalconception of value, since a situation's value as a part is defined interms of the overall intrinsic value of a complex situation to which itmakes a contribution beyond its own intrinsic value. Nonetheless thispoint implies that a thing's intrinsic value is not simply its valueirrespective of its consequences; it is also its value irrespective ofits context. Hence the concept of intrinsic value is to be such that atype of situation has the same intrinsic value in all contexts —which is why Moore holds that its intrinsic value depends only on its‘intrinsic nature’.

There are two connected problems here: the first concerns the way inwhich something's ‘value as a part’ depends on acceptingthat when it occurs as an element of a complex situation it may affectthe latter's value in a way which is not simply the result of takingits intrinsic value into account. This judgement is enshrined by Moorein his ‘principle of organic unities’, which declares thatthis kind of non-aggregative valuation of complex situations is liableto occur. The problem here is not that Moore's principle is incorrect,but rather that it seems irrational since it puts a block on moralreasoning. The second problem concerns the thesis that intrinsic valueis the same in all contexts. For this just seems wrong, in that thevalue of, say, friendship differs from one context to another.Although, as Moore rightly says, friendship is normally one of the mostvaluable things there is, it has no value at all where claims ofjustice are at stake, as in a court of law. So Moore's conception ofabsolutely universal intrinsic values should be replaced by aconception which allows for the ‘bracketing’ of normalvalues in certain contexts; and once this is in place, along with amore sophisticated account of normative values than Moore provides, itis reasonable to hope that the phenomena captured by Moore's irrationalprinciple of organic unities will find a more comprehensibleinterpretation.

Another area where Moore's ethical theory is problematic is hisaccount of ethical knowledge. Because of his hostility to ethicalnaturalism Moore denies that ethical knowledge is a matter of empiricalenquiry. But, as we have seen, he is equally hostile to Kant'srationalist thesis that fundamental ethical truths are truths ofreason. Instead he holds that ethical knowledge rests on a capacity foran intuitive grasp of fundamental ethical truths for which we can giveno reason since there is no reason to be given. The trouble with thisis that if we can say nothing to support a claim to such knowledge,those who disagree with it can only register their disagreement andpass on; hence ethical debate is liable to turn into the expression ofconflicting judgements which admit of no resolution. In the light ofthis, it is not surprising that Moore's ethical theory was regarded asundermining the cognitive status of morality, and thus that it leddirectly to the development of ethical non-cognitivism by those whowere influenced by Moore, such as A. J. Ayer and C. L. Stevenson. Yetthere was another side to Moore's discussion of ethical issues, inwhich he found himself arguing against the hedonist thesis thatpleasure is the only thing with positive intrinsic value, despite thefact that officially he held that no such arguments could be given.When engaged in this kind of ‘indirect’ method of argument,Moore sees himself as seeking to obtain agreement rather than toestablish the truth, though he also acknowledges that from afirst-person point of view there is little difference here. Becausethis indirect method is not integrated into his official method ofethical inquiry, he says little about its presuppositions. But it seemsto me that one can find here the beginnings of a ‘commonsense’ approach to ethics which is distinctly preferable to hisofficial appeal to intuitive judgments concerning the relativeintrinsic value of situations of arbitrary complexity.

So far I have discussed Moore's ‘metaethics’, his viewsabout the metaphysics of ethical value and the nature of ethicalknowledge. This emphasis reflects the fact that this aspect of Moore'sethical theory has been most influential; but it is also worthmentioning briefly some points from his moral theory. Moore presents astraightforward consequentialist account of the relationship betweenthe right and the good: the right action is that which will produce thebest outcome. In practice, because it is so difficult for us todetermine by ourselves what is the best outcome, he allows that weprobably do best if we follow established rules; thus Moore ends uprecommending a conservative form of rule consequentialism, for which hewas criticised by Keynes and Russell. Later critics such as W. D. Rossargued that because Moore subjects our personal responsibilities to theimpersonal test of producing the best outcome his position does notadequately capture the way in which they arise from our relationshipswith particular people; as recent critics put it, Moore's moral theoryis resolutely ‘agent-neutral’ and for that reasoninadequate as an account of the personal responsibilities which involveirreducibly ‘agent-relative’ values.

Finally, in the last chapter ofPrincipia Ethica,Moore setsout his ‘ideal’ — a deliberately unsystematic list ofintrinsic goods (such as friendship and the appreciation of beauty) andintrinsic evils (such as consciousness of pain). Moore's choice ofvalues is striking: it connects with the ‘Bloomsbury’ idealof life devoted to Art and Love, and excludes social values such asequality and freedom. The individualism of the resulting morality isenhanced by the fact that Moore maintains that these intrinsic valuesare incommensurable, and thus that the assessment of priorities amongthem is inescapably a matter of individual judgment. As Keynes put it,Moore's ideal was a kind of secular ‘religion’ - not muchuse for public policy but fine for talented individuals who could agreeto differ in their detailed value judgments.

4. Philosophical Analysis

By the time Moore returned to Cambridge in 1911 to a lectureshipthere, Russell  and Whitehead were finishing off their massiveproject of exhibiting the logical foundations of mathematics —Principia Mathematica. Although Moore was neither amathematician nor a logical theorist he was one of the first people tograsp that Russell's new logical theory was an essential tool forphilosophy and offered important new insights. One example of thisconcerns the status of propositions, the ‘objects’ ofthought. As we saw above, in his early work Moore had been emphaticthat propositions are altogether independent of thought and had evenproposed that facts are just true propositions. But as he came to thinkmore about falsehood in his lecturesSome Main Problems ofPhilosophy of 1910–11, it became clear to him that thisposition was a mistake, since the truth of a proposition should notaffect its  ontological status and yet it would be absurd to givefalse propositions the status of facts. So he now rejected the viewthat facts are just true propositions. On his new view, facts are, asbefore, constituted by objects and their properties; but what aboutpropositions? According to Moore, philosophers talk legitimately ofpropositions in order to identify the aspects of thought and languagewhich are crucial to questions of truth and inference, and in doing soit may appear that they regard propositions as genuine entities. But,Moore now holds, this implication is unwarranted: the mistake here isone of supposing that ‘every expression which seems to be a nameof something must be so in fact’ (Some Main Problems ofPhilosophy, 266). Moore does not allude here explicitly toRussell's theory of incomplete symbols and logical fictions, but it isclear that this is the kind of position he has in mind. The new logicenables one to preserve realist appearances without accepting realistmetaphysics.

Yet Moore was not an uncritical follower of Russell. He was criticalof Russell's account of implication in which Russell proposes that thetruth-functional conditional expresses all there is to the logicalrelationship of implication between propositions, and introducedinstead the term ‘entailment’ for this latter relationship(‘External and Internal Relations’ 90ff.). Whilerecognising that entailment is closely connected to logical necessityhe came to think that entailment is not just a matter of the necessityof the truth-functional conditional, thereby setting off a debate aboutthis relationship which continues to this day. Again, Moore wascritical of Russell's treatment of existence, in particular his denialthat it makes sense to treat existence as a first-order predicate ofparticular objects (for Russell, existence has to be expressed by theexistential quantifier and is therefore a second-order predicate ofpredicates). While agreeing with Russell that existence is not astraightforward first-order predicate (so that the logical form of‘Tame tigers exist’ is not the same as that of ‘Tametigers growl’), Moore argued that statements such as ‘Thismight not exist’ make perfectly good sense and that they couldnot do so unless the simpler statement ‘This exists’ alsomakes sense (‘Is Existence a Predicate?’ 145).

Moore's uses of Russell's logic take place in the broader context ofhis use of analysis as a method of philosophy. Although Moore alwaysdenied that philosophy is just analysis, there is no denying that itplays a central role in his philosophy and it is therefore important todetermine what motivates this role. This question is especiallypressing in Moore's case because he rejected the main analyticalprogrammes of twentieth century philosophy — both Wittgenstein'slogical atomism and the logical empiricism of the members of the Viennacircle and their followers such as A. J. Ayer. In the first case, Moorerejected Wittgenstein's thesis that whatever exists exists necessarily;as with the idealist thesis that all relations are internal, Moore heldthat our common sense conviction that some of the things which existmight not have done so creates a strong presumption against anyphilosopher who maintains the opposite, and that the logical atomistposition does not provide convincing reasons why this presumptionshould be overturned. In addition Moore held that it is just not truethat all necessity is logical necessity, as Wittgenstein maintained; inhis early writings, despite his hostility to Kant, he had explicitlydefended the conception of necessary synthetic truths and he did notchange his mind on this point. This point also provides a reason forhis rejection of logical empiricism, since this position famouslyincludes the thesis that all necessary truths are‘analytic’. But Moore also recognised that his earlycriticisms of William James' pragmatism can be applied to the logicalempiricist position. In connection with James, Moore had observed thatwhere a proposition concerns the past, it may well be that we are in asituation in which a proposition and its negation are both unverifiablebecause there is now no evidence either way on the matter. But, heargued, it does not follow that we cannot now affirm that either theproposition or its negation is true, thanks to the Law of ExcludedMiddle; in which case it cannot be that truth is verifiability —contrary both to James' pragmatism and to logical empiricism.

Yet why then did Moore think that the analysis of propositions wasso important? In part his motivation derives from his acceptance of aprinciple which Russell had introduced — that ‘everyproposition which we can understand must be composed wholly ofconstituents with which we are acquainted’ (Russell 91). For thisprinciple motivates the ‘sense-datum analysis’ ofperception to which he devoted so much attention and which I shalldiscuss in a moment. In addition, when explaining the importance ofphilosophical analysis, he emphasized the importance of getting clearwhat is at issue in some debate; but an issue which he himself was notclear about was that of the implications of an analysis. In his earlywritings he took the view that in so far as the analysis of aproposition clarifies it, it also clarifies its ontologicalimplications; thus he then held it to be an objection to aphenomenalist analysis of propositions about material objects that theanalysis calls into question the existence of such objects. But helater took the opposite point of view, maintaining that a phenomenalistanalysis just provides an account of what their existence amounts to.In between these two positions, in his 1925 paper ‘A Defence ofCommon Sense’ (which I discuss further below), Moore had heldthat what the sense-datum analysis of perception shows is thatsense-data are the ‘principal or ultimate subject<s>’(128) of propositions about perception. This remark, I think, reflectsthe true importance of philosophical analysis for Moore: its importancefor him is metaphysical in so far as it reveals the‘ultimate’ substances which are the subjects of ourordinary common sense thought and talk.

5. Perception and Sense-data

It did not take Moore long to realise that the realist position hehad advanced in ‘The Refutation of Idealism’ was too‘na•ve’ to be tenable; he had to be able toaccommodate ‘false’ appearances somehow. But the strategyMoore adopted to deal with this remained true to the basic thesis of‘The Refutation of Idealism’ that one should account forthe appearances of things in terms of the properties of the primaryobjects of experience, and not the qualities of experiences themselves.To elaborate this position Moore introduced the term‘sense-datum’ to describe these primary objects ofexperience:

But now, what happened to each of us, when we saw thatenvelope? I will begin by describingpart of what happened tome. I saw a patch of a particular whitish colour, having a certainshape …. These things: this patch of a whitish colour, and itssize and shape I did actually see. And I propose to call these things,the colour and size and shape,sense-data … (SomeMain Problems of Philosophy 30)

Moore implies here that the colour, shape and size are distinctsense-data; but he soon revised his terminology so that these areregarded as properties of the visual sense-datum he ‘actuallysaw’, or ‘directly apprehended’ as he normallysays.

Once the concept of a sense-datum has been introduced in this way,it is easy to see that false appearances can be handled bydistinguishing between the properties of sense-data we apprehend andthe properties of the physical objects which give rise to thesesense-data. But what is the relationship between sense-data andphysical objects? Moore took it that there are three serious candidatesto be considered: (i) an indirect realist position, according to whichsense-data are non-physical but somehow produced by interactionsbetween physical objects and our senses; (ii) the phenomenalistposition, according to which our conception of physical objects ismerely one which expresses observed and anticipated uniformities amongthe sense-data we apprehend; (iii) a direct realist position, accordingto which sense-data are parts of physical objects — so that, forexample, visual sense-data are visible parts of the surfaces ofphysical objects. The indirect realist position is that to which he wasinitially drawn; but he could see that it leaves our beliefs about thephysical world exposed to skeptical doubt, since it implies that theobservations which constitute evidence for these beliefs concern onlythe properties of non-physical sense-data, and there is no obvious wayfor us to obtain further evidence to support a hypothesis about theproperties of the physical world and its relationship to oursense-data. This argument is reminiscent of Berkeley's critique ofLocke, and Moore therefore considered carefully Berkeley'sphenomenalist alternative. Moore's initial response to this positionwas that the implied conception of the physical world was just too‘pickwickian’ to be believable. This may be felt to be toointuitive, like Dr. Johnson's famous objection to Berkeley; but Moorecould also see that there were substantive objections to thephenomenalist position, such as the fact that our normal ways ofidentifying and anticipating significant uniformities among oursense-data draw on our beliefs about our location in physical space andthe state of our physical sense-organs, neither of which are availableto the consistent phenomenalist.

So far Moore's dialectic is familiar. What is unfamiliar is hisdirect realist position, according to which sense-data are physical.This position avoids the problems so far encountered, but in order toaccommodate false appearances Moore has to allow that sense-data maylack the properties which we apprehend them as having. It may be feltthat in so far as sense-data are objects at all, this is inevitable;but Moore now needs to provide an account of the apparent properties ofsense-data and it is not clear how he can do this without going back onthe initial motivation for the sense-datum theory by construing theseapparent properties as properties of our experiences. But what in factturns Moore against this direct realist position is the difficulty hethinks it leads to concerning the treatment of hallucinations. In suchcases, Moore holds, any sense-data we apprehend are not parts of aphysical object; so direct realism cannot apply to them, and yet thereis no reason to hold that they are intrinsically different from thesense-data which we apprehend in normal experience. This last pointmight well be disputed, and at one point Moore himself considers thepossibility of a distinction between ‘subjective’ and‘objective’ sense-data; but once one has introducedsense-data in the first place as the primary objects of experience itis not going to be easy to make a distinction here without assumingmore about experience than Moore at any rate would have wanted toconcede.

Moore wrote more extensively about perception than about any othertopic. In these writings he moves between the three alternatives setout here without coming to any firm conclusion. From the outside, itseems clear that what was leading him astray was the sense-datumhypothesis itself and his reflections on perception can be regarded asan extendedreductio ad absurdum of this hypothesis. It wasonly towards the end of his career that he encountered in Ducasse'sadverbial theory a serious alternative to the sense-datum hypothesis.But the adverbial theory provides no easy way of avoiding thedifficulties Moore confronted: Moore rightly objected to Ducasse thatit is not at all clear how the structure of a sensory field can beconstrued in adverbial terms. Yet there were other alternatives: inparticular, from the start of the twentieth century thephenomenological movement had offered an account of perception basedupon a recognition of its inherent intentionality which avoids some ofthe pitfalls of the sense-datum theory. It is, I think, a pity thatMoore did not engage with this position, but this detachment was alltoo characteristic of the relationship at the time between theanalytical and phenomenological traditions.

6. Common Sense and Certainty

An important aspect of Moore's rejection of idealism was hisaffirmation of a ‘common sense’ realist position, accordingto which our ordinary common-sense view of the world is largelycorrect. Moore first explicitly championed this position in his 1910-11lecturesSome Main Problems of Philosophybut he made it hisown when he responded in 1925 to an invitation to describe his‘philosophical position’ by setting this out as ‘ADefence of Common Sense’. Moore begins the paper by listing alarge number of ‘truisms’ such as that ‘the earth hadexisted also for many years before my body was born’. Concerningthese truisms he then asserts, first, that he knows them for certain,second, that other people likewise know for certain the truth ofcomparable truisms about themselves and, third, that he knows thissecond general truth (and, by implication, others do too). So the truthand general knowledge of these truisms is a matter of common sense.Having set out these truisms, Moore then acknowledges that somephilosophers have denied their truth or, more commonly, denied ourknowledge of them (even though, according to Moore, they also knowthem) and he attempts to show that these denials are incoherent orunwarranted. These claims might seem to leave little space for radicalphilosophical argument. But in the last part of the paper Moore arguesthat his defence of common sense leaves completely undecided thequestion as to how the truistic propositions which make up the commonsense view of the world are to be analysed; the analysis may be asradical as one likes as long as it is consistent with the truth andknowability of the propositions analysed. Thus, for example, he iscontent to allow that philosophical argument may show that aphenomenalist analysis of propositions about the physical world iscorrect.

This last point shows that Moore's defence of common sense is not asmuch of a constraint on philosophical theory as one might at first havethought; for philosophical analysis can reveal to us facts about the‘principal or ultimate subject’ of a truistic propositionwhich are by no means what common sense supposes. This implication isimportant when one turns to consider Moore's most famous paper, his‘Proof of an External World’ — the text of a BritishAcademy lecture delivered in 1939 just when Moore was retiring from hisCambridge Professorship. Moore here sets himself the task of doing whatKant had earlier set himself to do, namely providing a proof of theexistence of ‘external objects’. Much of the lecture isdevoted to working out what counts as an ‘external object’,and Moore claims that these are things whose existence is not dependentupon our experience. So, he argues, if he can prove the existence ofany such things, then he will have proved the existence of an‘External World’. Moore then maintains that he can do this—

How? By holding up my two hands, and saying, as I make acertain gesture with the right hand, ‘Here is one hand’,and adding, as I make a certain gesture with the left, ‘and hereis another’ (‘Proof of an External World’166).

Moore then goes to argue that this demonstration of his hands was a‘perfectly rigorous’ proof of the existence of externalobjects. For its premises certainly entail its conclusion and they arethings which he then knew to be true —

Iknew that there was one hand in the placeindicated by combining a certain gesture with my first utterance of‘here’ and that there was another in the different placeindicated by combining a certain gesture with my second utterance of‘here’. How absurd it would be to suggest that I did notknow it, but only believed it, and that perhaps it was not the case!You might as well suggest that I do not know that I am now standing upand talking — that perhaps after all I'm not, and that it's notquite certain that I am! (‘Proof of an External World’166)

The significance of this performance has been debated ever sinceMoore set it out. It is commonly supposed that Moore here sets himselfto refute philosophical skepticism; and that his performance, thoughintriguing, is unsuccessful. But this interpretation is incorrect:Moore's avowed aim is to provethe existence of an externalworld, not to provehis knowledge of the existence of anexternal world. Moore himself set this out clearly in a subsequentdiscussion of his lecture:

I have sometimes distinguished between two differentpropositions, each of which has been made by some philosophers, namely(1) the proposition ‘there are no material things’ and (2)the proposition ‘Nobody knows for certain that there are anymaterial things’. And in my latest British Academy lecture called‘Proof of an External World’ … I implied with regardto the first of these propositions that it could beproved tobe false in such a way as this; namely, by holding up one of your handsand saying ‘This hand is a material thing; thereforethere is at least one material thing’. But with regard to thesecond of the two propositions …. I do not think I have everimplied thatit could beproved to be false in anysuch simple way … (‘A Reply to my Critics’668)

Setting aside any anti-skeptical intent therefore, what needsassessment is the metaphysical significance of Moore's proof, as aproof of an ‘external world’. Clearly, everything heredepends on what is to count as ‘external’, in particularwhether Moore's demonstration of the existence of his hands proves theexistence of things that are in no way at all dependent upon experienceor thought. It is, I think, obvious that it does not; for that issue isone which depends on broader philosophical questions about idealismwhich cannot possibly be settled that way. Moore's own distinctionbetween questions of truth and questions of analysis should beintroduced here. Moore's ‘proof’ demonstrates the‘empirical’ truth of a simple truism, that he has hands;but it leaves entirely open the question of the analysis of thistruism. Yet it is at the level of analysis that the‘transcendental’ question of whether things such as handsare altogether independent of experience and thought is to beanswered.

Although, as I have indicated, Moore did not intend his‘proof’ as a refutation of skepticism, he did frequentlyargue against skeptical views; and in his early writings, despite thepassage quoted just now, he does sometimes give the impression that hethinks one can refute skepticism by simply bringing forward astraightforward case of knowledge, such as ‘I know that this is apencil’. But on examination it turns out that his strategy hereis more subtle; he wants to argue that we get our understanding ofknowledge primarily through straightforward cases of this kind, andthus that skeptical arguments are self-undermining: for, on the onehand, they rely on general principles about the limits of knowledge andthus assume some understanding of knowledge but, on the other hand,they undermine this understanding by implying that there are no suchstraightforward cases of it. The force of arguments of this kind is,however, disputable, since the skeptic can always present his argumentas areductio ad absurdum of the possibility of knowledge; andthe same point applies to Moore's other attempts to convict the skepticof some kind of pragmatic incoherence.

In two of his last writings, ‘Four Forms of Skepticism’and ‘Certainty’, Moore, perhaps dissatisfied with theseearlier arguments and with the misunderstanding of his‘proof’, returned to the issue and set himself thechallenge of refuting Cartesian skepticism. Notoriously, by the end of‘Certainty’ Moore acknowledges defeat: having agreed thatif he does not know that he is not dreaming, then he does not know suchthings as that he is standing up and talking, he accepts (withreservations) that he cannot know for certain that he is not dreaming.Most commentators agree that Moore lost his way here. But it is notclear where, since Moore makes no obvious mistake. Nonetheless theviability of a ‘common sense’ response to skepticismremains an important feature of later discussions of the topic. Moorewas clearly right when, for example, he remarked that despite Russell'sfrequent skeptical professions, Russell was nonetheless perfectly sure,without a shadow of doubt, on thousands of occasions, that he wassitting down. But what is difficult to achieve here is a formulation ofthe skeptical dialectic which both shows the importance of Moore's‘common sense’ affirmations of certainty and yet avoids adogmatic insistence that knowledge does not need to be vindicated inthe face of skeptical argument. I myself think that Wittgenstein'swritingsOn Certainty, which were much influenced by Moore,best indicate how this is to be achieved, but this is not the place todemonstrate this achievement.

7. Moore's Legacy

Moore was not a systematic philosopher: unlike Reid's philosophy ofcommon sense, Moore's ‘common sense’ is not a system. Evenin ethics, where he comes closest to presenting a ‘theory’he explicitly disavows any aspiration to provide a systematic accountof the good. Hence, as the preceding discussions show, Moore's legacyis primarily a collection of arguments, puzzles and challenges. Onenotable addition to those mentioned already is ‘Moore'sparadox’: if I am mistaken about something, then I believesomething which is not the case — perhaps that it is raining whenit is not. Yet if I attribute this mistake to myself by saying‘It's not raining but I believe that it is’ my statement isabsurd. Why is this so? Why is it absurd for me to say something thatit is true about myself? Moore himself thought that the explanationhere was just that we generally believe the things we say, so that whensaying ‘It's not raining’ I imply that I believe this; butWittgenstein rightly saw that this explanation was superficial and thatMoore had put his finger on a much deeper phenomenon here whichconcerns our sense of our own identity as thinkers.

This case is typical. Moore had an unparalleled ability foridentifying philosophical ‘phenomena’. His own discussionsof their significance are not always satisfying; but he would be thefirst to acknowledge his own fallibility. What matters is that if westart where he starts we can be sure that we are dealing with somethingthat will tell us something important about ourselves and theworld.

Bibliography

Primary Sources

[* indicates the edition used for page references in this entry]

• ‘The Nature of Judgment’Mind 8 (1899) 176-93.Reprinted in *G. E. Moore: Selected Writings1-19.
• ‘Truth’ in J. Baldwin (ed.)Dictionary ofPhilosophy and Psychology Macmillan, London: 1901-2. Reprinted in*G. E. Moore: Selected Writings 20-2.
• ‘The Refutation of Idealism’Mind 12 (1903)433-53. Reprinted inPhilosophical Studies and in *G. E.Moore: Selected Writings23-44.
• Principia Ethica Cambridge University Press, Cambridge:1903. *Revised edition with ‘Preface to the second edition’and other papers, ed. T. Baldwin, Cambridge University Press,Cambridge: 1993.
• Ethics Williams & Norgate, London: 1912.
• ‘External and Internal Relations’Proceedings ofthe Aristotelian Society20 (1919-20) 40-62. Reprinted inPhilosophical Studies and in *G. E. Moore: SelectedWritings 79-105.
• ‘The Conception of Intrinsic Value’ inPhilosophical Studies. Reprinted in *Revised edition ofPrincipia Ethica,  280-98.
• Philosophical Studies K. Paul, Trench, Trubner & Co,London: 1922.
• ‘A Defence of Common Sense’ in J. H. Muirhead(ed.)Contemporary British Philosophy (2nd series), Allen andUnwin, London: 1925, 193-223. Reprinted inPhilosophicalPapers and in *G. E. Moore: Selected Writings106-33.
• ‘Is Existence a Predicate?’Aristotelian SocietySupplementary volume 15 (1936) 154-88. Reprinted inPhilosophical Papers and in *G. E. Moore: SelectedWritings 134-46.
• ‘Proof of an External World’Proceedings of theBritish Academy 25 (1939) 273-300. Reprinted inPhilosophicalPapers and in *G. E. Moore: Selected Writings147-70.
• ‘A Reply to My Critics’ in P. A. Schilpp (ed.)ThePhilosophy of G. E. Moore Northwestern University Press, EvanstonILL: 1942, 535-677.
• Some Main Problems of Philosophy George, Allen and Unwin,London: 1953.
• ‘Certainty’ inPhilosophical Papers 226-251.Reprinted in *G. E. Moore: Selected Writings 171-96.
• Philosophical Papers George, Allen and Unwin, London:1959.
• The Elements of Ethics, T. Regan (ed.), Temple UniversityPress, Philadelphia PA: 1991.
• G. E. Moore: Selected Writings, T. Baldwin (ed.),Routledge, London: 1993.

For a complete bibliography of Moore's published writings up to 1966,see P. A. Schilpp (ed.)The Philosophy of G. E. MooreNorthwestern University Press, Evanston ILL: 1942, 691-701.

Secondary Sources

General

• P. A. Schilpp (ed.)The Philosophy of G. E. MooreNorthwestern University Press, Evanston ILL: 1942.
• A. Ambrose and M. Lazerowitz (eds.)G. E. Moore: Essays inRetrospect Allen and Unwin, London: 1970.
• T. BaldwinG. E. Moore Routledge, London: 1990.

Section 1. Life and Career

• J. M. Keynes ‘My Early Beliefs’ inTwo MemoirsHart-Davis, London: 1949.
• G. Ryle ‘G. E. Moore’ inCollected Papers I,Hutchinson, London: 1971.

Section 2. The Refutation of Idealism

• C. Ducasse ‘Moore's Refutation of Idealism’ in P. A.Schilpp (ed.)The Philosophy of G. E. Moore.
• P. HyltonRussell, Idealism and the Emergence of AnalyticPhilosophy Oxford University Press, Oxford: 1990.

Section 3.Principia Ethica

• C. D. Broad ‘Certain Features in Moore's EthicalDoctrines’ in P. A. Schilpp (ed.)The Philosophy of G. E.Moore.
• W. J. Frankena ‘Obligation and Value in the Ethics of G. E.Moore’ in P. A. Schilpp (ed.)The Philosophy of G. E.Moore.
• W. J. Frankena ‘The Naturalistic Fallacy’Mind48 (1939).
• N. M. LemosIntrinsic Value. Cambridge University Press,Cambridge: 1994.
• W. D. RossThe Right and the Good Oxford University Press,Oxford: 1930.
• N. Sturgeon ‘Ethical Intuitionism and EthicalNaturalism’ in P. Stratton-Lake (ed.)EthicalIntuitionism Oxford University Press, Oxford: 2002.
• Ethics 113 (2003) — special edition for centenary ofPrincipia Ethica
• The Journal of Value Inquiry 37 (2003) — specialedition for centenary ofPrincipia Ethica.

Section 4. Philosophical Analysis

• B. RussellThe Problems of Philosophy, Williams andNorgate, London: 1912.
• N. Malcolm ‘Moore and Ordinary Language’ in P. A.Schilpp (ed.)The Philosophy of G. E. Moore.
• J. Wisdom ‘Moore's Technique’ in P. A. Schilpp (ed.)The Philosophy of G. E. Moore.

Section 5. Perception and Sense-data

• O. K. Bowsma ‘Moore's Theory of Sense-data’ in P. A.Schilpp (ed.)The Philosophy of G. E. Moore.
• R. Chisholm ‘The Theory of Appearing’ in R. Swarz (ed.)Perceiving, Sensing and Knowing Doubleday & Co., GardenCity NY: 1965, 168-86.
• G. A. Paul ‘Is There a Problem about Sense-Data?’ in R.Swarz (ed.)Perceiving, Sensing and Knowing Doubleday &Co., Garden City NY: 1965, 271-87.

Section 6. Common Sense and Certainty

• T. Clarke ‘The Legacy of Skepticism’Journal ofPhilosophy (1972).
• N. Malcolm ‘Defending Common Sense’PhilosophicalReview (1949).
• N. Malcolm ‘Moore and Wittgenstein on the sense of “IKnow”’ inThought and Language, Cornell UniversityPress, Ithaca NY: 1977.
• M. McGinnSense and Certainty Blackwell, Oxford:1989.
• A. StrollMoore and Wittgenstein Oxford University Press,New York: 1994.
• B. StroudThe Significance of PhilosophicalSkepticismOxford University Press, Oxford: 1984.
• L. WittgensteinOn Certainty Blackwell, Oxford: 1969.
• C. J. Wright ‘Facts and Certainty’Proceedings ofthe British Academylxxi (1985) 429-72.

Section 7. Moore's Legacy

• L. WittgensteinPhilosophical Investigations Blackwell,Oxford: 1953 (see part II section x for ‘Moore'sparadox’).

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