Why is it rational to believe scientific theories are true?

Abstract

Alan Musgrave is one of the foremost contemporary defenders of scientific realism. He is also one of the leading exponents of Karl Poppers critical rationalist philosophy. In this paper, my main focus will be on Musgraves realism. However, I will emphasize epistemological aspects of realism. This will lead me to address aspects of his critical rationalism as well. Musgrave is both a scientific realist and a commonsense realist. Scientific realism, he says, is a form of realism (1999, p. 132). And realism is committed to the commonsense realist belief that there is a real world outside of us and largely independent of us (1999, p. 132). There is, Musgrave adds, a continuity between common sense and science (1999, p. 132). But while science may lead to occasional revision and refinement of common sense, it does not show that it is root-and-branch mistaken (1999, p. 133; cf. 1996, p. 23). The real world postulated by common sense is the reality that science seeks to explain. This world does not depend on human belief or experience. Nor is it relative to conceptual scheme, theoretical background or mode of description (1999, pp. 52, 173, 180 ff). For Musgrave, though, realism is not just a thesis about reality. It is also a thesis about truth. Musgrave takes the aim of science to be truth. He subscribe[s] to the old-fashioned idea that scientific realism ... says that the aim of a scientific inquiry is to discover the truth about the matter inquired into (1996, p. 19; cf. 1999, p. 52). Scientific theories are taken at face-value as genuine assertions about the world, the truth or falsity of which depends on the way the world really is (1996, p. 26). Musgrave understands truth in the classic correspondence sense that he takes to have been defined by Tarski. A theory or statement is true just in case the world is the way it is said to be (1993, ch. 14; 1996, p. 24; 1999, p. 165). This is a nonepistemic conception of truth (1996, p. 28; cf. 1999, p. 186). Given the emphasis on correspondence between theory and reality, Musgraves realism diverges from the tendency among some scientific realists to adopt ontological rather than truthorientated versions of the doctrine. Musgrave dismisses such entity-realism as incoherent (1996, p. 20).1 Musgraves realism has an epistemological dimension as well. For Musgrave, methodological considerations play a prominent role in the appraisal and acceptance of scientific theories. While a variety of methodological norms figures in Musgraves writings, there is some tendency on his part to emphasize the testing and falsification of theories.2 The attempt to falsify theories is the basis of the critical method in science. And criticism is the heart of rationality. A critical discussion may provide the best reason there is for believing (tentatively) that a hypothesis is true (1999, p. 324). If a theory best withstands criticism then it is reasonable for scientists to believe that theory and to use it in practical applications (1999, p. 325). Such belief must remain tentative, however. For Musgrave is a fallibilist who eschews the search for epistemic certainty in science and everyday affairs (cf. 1993, ch. 15; 1999, pp. 194 ff, 341-3). But matters of method and rationality are separate matters from those of reality and truth. This is especially the case from the perspective of realism. In the first place, to believe that the world is a given way does not mean that the world is that way. Nor does it make the world that way. Reality is not subject to determination by human thought. This remains the case even if the belief that the world is a given way is a belief that is rationally justified. For one may rationally believe what is false. The point applies with equal force to scientific theories certified by the norms of scientific method. A theory that is certified by the norms of method is not thereby shown to be true. A theory which satisfies methodological norms may yet be false. Nor need a theory that satisfies methodological norms be accepted as true. The methods of science are not the exclusive domain of realism. They may serve aims other than the realist aim of truth. Satisfaction of the norms of method might indicate empirical adequacy or pragmatic reliability, rather than truth. An explanation is therefore required on the part of the realist of why certification by method provides warrant with respect to truth. I will refer to the need to provide such an explanation as the problem of method and truth. As a realist who holds that it may be rational to believe a theory which has been subjected to critical scrutiny in accordance with the norms of method, the problem of method and truth is one that Musgrave must address. That is, he must confront the question of why it is rational to believe theories certified by the methods of science to be true, or close to the truth.3 In this paper, I will explore his response to the problem. I will illustrate the problem of method and truth in section 2 by means of the examples of Lakatoss plea for a whiff of inductivism and the internal realist conception of truth of Putnam and Ellis. In section 3, I will turn to Musgraves approach to the problem of method and truth, where I will consider his treatment of inference to best explanation and critical rationalism. In section 4, I will explore a naturalistic approach to the problem which sets the issue within a broader metaphysical framework. Finally, in section 5, I shall offer some suggestions as to how Musgrave might put metaphysical aspects of his realist position to epistemological use. © 2006 Springer.