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Scientific realism is the philosophical view that the universe described by science (including both observable and unobservable aspects) exists independently of our perceptions, and that verified scientific theories are at least approximately true descriptions of what isreal.[1] Scientific realists typically assert that science, when successful, uncovers true (or approximately true) knowledge about nature, including aspects of reality that are not directly observable.[1]
Withinphilosophy of science, this view is often an answer to the question "how is the success of science to be explained?" The discussion on the success of science in this context centers primarily on the status ofunobservable entities apparently talked about by scientifictheories. Generally, those who are scientific realists assert that one can make valid claims about unobservables (viz., that they have the sameontological status) as observables, as opposed toinstrumentalism.
In a 2020 PhilPapers Survey 72% of academic philosophers favored scientific realism vs only 15% favoring antirealism.[2]
Scientific realism involves two basic positions:
Realists often adopt this thesis selectively; one may be realist about mature fields such as fundamental physics while remaining agnostic about less-settled areas.[5]
An ideal scientific theory, on the realist view, satisfies three interconnected commitments:[6]
Taken together, the first two commitments imply that an ideal theory makes definite assertions about genuinely exists entities, while the third justifies believing a significant subset of those assertions.
Realists therefore argue that science progresses: later theories generally answer more questions or do so more accurately, thus moving closer, though never necessarily reaching, the ideal of a literally true account of nature.[7]
The following claims are typical of those held by scientific realists. Due to the wide disagreements over the nature of science's success and the role of realism in its success, a scientific realist would agree with some but not all of the following positions.[8]
Scientific realism is related to much older philosophical positions includingrationalism andmetaphysical realism. However, it is a thesis about science developed in the twentieth century. Portraying scientific realism in terms of its ancient, medieval, and early modern cousins is at best misleading.
Scientific realism is developed largely as a reaction tological positivism. Logical positivism was the first philosophy of science in the twentieth century and the forerunner of scientific realism, holding that a sharp distinction can be drawn betweentheoretical terms andobservational terms, the latter capable of semantic analysis in observational and logical terms.
Logical positivism encountered difficulties with:
These difficulties for logical positivism suggest, but do not entail, scientific realism, and led to the development of realism as a philosophy of science.
Realism became the dominant philosophy of science after positivism.[9]: 70 Bas van Fraassen in his bookThe Scientific Image (1980) developedconstructive empiricism as an alternative to realism. He argues against scientific realism that scientific theories do not aim for truth about unobservable entities.[10] Responses to van Fraassen have sharpened realist positions and led to some revisions of scientific realism.
One of the main arguments for scientific realism centers on the notion that scientific knowledge is progressive in nature, and that it is able to predict phenomena successfully.[11] Many scientific realists (e.g.,Ernan McMullin,Richard Boyd) think the operational success of a theory lends credence to the idea that its more unobservable aspects exist, because they were how the theory reasoned its predictions. For example, a scientific realist would argue that science must derive someontological support for atoms from the outstanding phenomenological success of all the theories using them.
Arguments for scientific realism often appeal toabductive reasoning or "inference to the best explanation" (Lipton, 2004). For instance, one argument commonly used—the "miracle argument" or "no miracles argument"—starts out by observing that scientific theories are highly successful in predicting and explaining a variety of phenomena, often with great accuracy. Thus, it is argued that the best explanation—the only explanation that renders the success of science to not be whatHilary Putnam calls "a miracle"—is the view that our scientific theories (or at least the best ones) provide true descriptions of the world, or approximately so.[12]
Bas van Fraassen replies 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 any scientific theory is born into a life of fierce competition, a jungle red in tooth and claw. Only the successful theories survive—the ones which in fact latched on to actual regularities in nature." (The Scientific Image, 1980)
It has been argued that the no miracles argument commits thebase rate fallacy.[13]
Pessimistic induction, one of the main arguments against realism, argues that the history of science contains many theories once regarded as empirically successful but which are now believed to be false. Additionally, the history of science contains many empirically successful theories whose unobservable terms are not believed to genuinely refer. For example, the effluvium theory of static electricity (a theory of the 16th Century physicistWilliam Gilbert) is an empirically successful theory whose central unobservable terms have been replaced by later theories.
Realists reply that replacement of particular realist theories with better ones is to be expected due to the progressive nature of scientific knowledge, and when such replacements occur only superfluous unobservables are dropped. For example,Albert Einstein's theory ofspecial relativity showed that the concept of theluminiferous ether could be dropped because it had contributed nothing to the success of the theories ofmechanics andelectromagnetism. On the other hand, when theory replacement occurs, a well-supported concept, such as the concept ofatoms, is not dropped but is incorporated into the new theory in some form. These replies can lead scientific realists tostructural realism.
Social constructivists might argue that scientific realism is unable to account for the rapid change that occurs inscientific knowledge during periods ofscientific revolution. Constructivists may also argue that the success of theories is only a part of the construction.
However, these arguments ignore the fact that many scientists are not realists. During the development ofquantum mechanics in the 1920s, the dominant philosophy of science waslogical positivism. The alternative realistBohm interpretation andmany-worlds interpretation of quantum mechanics do not make such a revolutionary break with the concepts ofclassical physics.
Another argument against scientific realism, deriving from theunderdetermination problem, is not so historically motivated as these others. It claims that observational data can in principle be explained by multiple theories that are mutually incompatible. Realists might counter by saying that there have been few actual cases of underdetermination in the history of science. Usually the requirement of explaining the data is so exacting that scientists are lucky to find even one theory that fulfills it. Furthermore, if we take the underdetermination argument seriously, it implies that we can know about only what we have directlyobserved. For example, we could not theorize thatdinosaurs once lived based on thefossil evidence because other theories (e.g., that the fossils are clever hoaxes) can account for the same data.
According to the incompatible models argument, in certain cases the existence of diverse models for a single phenomenon can be taken as evidence of anti-realism.[14] One example is due toMargaret Morrison, who worked to show that theshell model and theliquid-drop model give contradictory descriptions of theatomic nucleus, even though both models are predictive.[15]
