the branch of philosophy that is centered on a critical examination of the sciences: their methods and their results. One branch of the philosophy of science, methodology, is closely related to the theory of knowledge. It explores the methods by which science arrives at its posited truths concerning the world and critically explores alleged rationales for these methods. Issues concerning the sense in which theories are accepted in science, the nature of the confirmation relation between evidence and hypothesis, the degree to which scientific claims can be falsified by observational data, and the like, are the concern of methodology. Other branches of the philosophy of science are concerned with the meaning and content of the posited scientific results and are closely related to metaphysics and the philosophy of language. Typical problems examined are the nature of scientific laws, the cognitive content of scientific theories referring to unobservables, and the structure of scientific explanations. Finally, philosophy of science explores specific foundational questions arising out of the specific results of the sciences. Typical questions explored might be metaphysical presuppositions of space-time theories, the role of probability in statistical physics, the interpretation of measurement in quantum theory, the structure of explanations in evolutionary biology, and the like. Concepts of the credibility of hypotheses. Some crucial concepts that arise when issues of the credibility of scientific hypotheses are in question are the following: Inductivism is the view that hypotheses can receive evidential support from their predictive success with respect to particular cases falling under them. If one takes the principle of inductive inference to be that the future will be like the past, one is subject to the skeptical objection that this rule is empty of content, and even self-contradictory, if any kind of ‘similarity’ of cases is permitted. To restore content and consistency to the rule, and for other methodological purposes as well, it is frequently alleged that only natural kinds, a delimited set of ‘genuine’ properties, should be allowed in the formulation of scientific hypotheses. The view that theories are first arrived at as creative hypotheses of the scientist’s imagination and only then confronted, for justificatory purposes, with the observational predictions deduced from them, is called the hypotheticodeductive model of science. This model is contrasted with the view that the very discovery of hypotheses is somehow ‘generated’ out of accumulated observational data. The view that hypotheses are confirmed to the degree that they provide the ‘best explanatory account’ of the data is often called abduction and sometimes called inference to the best explanation. The alleged relation that evidence bears to hypothesis, warranting its truth but not, generally, guaranteeing that truth, is called confirmation. Methodological accounts such as inductivism countenance such evidential warrant, frequently speaking of evidence as making a hypothesis probable but not establishing it with certainty. Probability in the confirmational context is supposed to be a relationship holding between propositions that is quantitative and is described by the formal theory of probability. It is supposed to measure the ‘degree of support’ that one proposition gives to another, e.g. the degree of support evidential statements give to a hypothesis allegedly supported by them.
Scientific methodologists often claim that science is characterized by convergence. This is the claim that scientific theories in their historical order are converging to an ultimate, final, and ideal theory. Sometimes this final theory is said to be true because it corresponds to the ‘real world,’ as in realist accounts of convergence. In pragmatist versions this ultimate theory is the defining standard of truth.
It is sometimes alleged that one ground for choosing the most plausible theory, over and above conformity of the theory with the observational data, is the simplicity of the theory. Many versions of this thesis exist, some emphasizing formal elements of the theory and others, e.g., emphasizing paucity of ontological commitment by the theory as the measure of simplicity.
It is sometimes alleged that in choosing which theory to believe, the scientific community opts for theories compatible with the data that make minimal changes in scientific belief necessary from those demanded by previously held theory. The believer in methodological conservatism may also try to defend such epistemic conservatism as normatively rational.
An experiment that can decisively show a scientific hypothesis to be false is called a crucial experiment for the hypothesis. It is a thesis of many philosophers that for hypotheses that function in theories and can only confront observational data when conjoined with other theoretical hypotheses, no absolutely decisive crucial experiment can exist.
Concepts of the structure of hypotheses. Here are some of the essential concepts encountered when it is the structure of scientific hypotheses that is being explored:
In its explanatory account of the world, science posits novel entities and properties. Frequently these are alleged to be not accessible to direct observation. A theory is a set of hypotheses positing such entities and properties. Some philosophers of science divide the logical consequences of a theory into those referring only to observable things and features and those referring to the unobservables as well. Various reductionist, eliminationist, and instrumentalist approaches to theory agree that the full cognitive content of a theory is exhausted by its observational consequences reported by its observation sentences, a claim denied by those who espouse realist accounts of theories. The view that the parts of a theory that do not directly relate observational consequences ought not to be taken as genuinely referential at all, but, rather, as a ‘mere linguistic instrument’ allowing one to derive observational results from observationally specifiable posits, is called instrumentalism. From this point of view terms putatively referring to unobservables fail to have genuine reference and individual non-observational sentences containing such terms are not individually genuinely true or false. Verificationism is the general name for the doctrine that, in one way or another, the semantic content of an assertion is exhausted by the conditions that count as warranting the acceptance or rejection of the assertion. There are many versions of verificationist doctrines that try to do justice both to the empiricist claim that the content of an assertion is its totality of empirical consequences and also to a wide variety of anti-reductionist intuitions about meaning. The doctrine that theoretical sentences must be strictly translatable into sentences expressed solely in observational terms in order that the theoretical assertions have genuine cognitive content is sometimes called operationalism. The ‘operation’ by which a magnitude is determined to have a specified value, characterized observationally, is taken to give the very meaning of attributing that magnitude to an object. The doctrine that the meanings of terms in theories are fixed by the role the terms play in the theory as a whole is often called semantic holism. According to the semantic holist, definitions of theoretical terms by appeal to observational terms cannot be given, but all of the theoretical terms have their meaning given ‘as a group’ by the structure of the theory as a whole. A related doctrine in confirmation theory is that confirmation accrues to whole theories, and not to their individual assertions one at a time. This is confirmational holism. To see another conception of cognitive content, conjoin all the sentences of a theory together. Then replace each theoretical term in the sentence so obtained with a predicate variable and existentially quantify over all the predicate variables so introduced. This is the Ramsey sentence for a (finitely axiomatized) theory. This sentence has the same logical consequences framable in the observational vocabulary alone as did the original theory. It is often claimed that the Ramsey sentence for a theory exhausts the cognitive content of the theory. The Ramsey sentence is supposed to ‘define’ the meaning of the theoretical terms of the original theory as well as have empirical consequences; yet by asserting the existence of the theoretical properties, it is sometimes alleged to remain a realist construal of the theory. The latter claim is made doubtful, however, by the existence of ‘merely representational’ interpretations of the Ramsey sentence.
Theories are often said to be so related that one theory is reducible to another. The study of the relation theories bear to one another in this context is said to be the study of intertheoretic reduction. Such reductive claims can have philosophical origins, as in the alleged reduction of material objects to sense-data or of spatiotemporal relations to causal relations, or they can be scientific discoveries, as in the reduction of the theory of light waves to the theory of electromagnetic radiation. Numerous ‘models’ of the reductive relation exist, appropriate for distinct kinds and cases of reduction.
The term scientific realism has many and varied uses. Among other things that have been asserted by those who describe themselves as scientific realists are the claims that ‘mature’ scientific theories typically refer to real features of the world, that the history of past falsifications of accepted scientific theories does not provide good reason for persistent skepticism as to the truth claims of contemporary theories, and that the terms of theories that putatively refer to unobservables ought to be taken at their referential face value and not reinterpreted in some instrumentalistic manner.
Internal realism denies irrealist claims founded on the past falsification of accepted theories. Internal realists are, however, skeptical of ‘metaphysical’ claims of ‘correspondence of true theories to the real world’ or of any notion of truth that can be construed in radically non-epistemic terms. While theories may converge to some ultimate ‘true’ theory, the notion of truth here must be understood in some version of a Peircian idea of truth as ‘ultimate warranted assertability.’
The claim that any theory that makes reference