Lecture 25: Scientific Explanation Logic, Science, and Society March 18, 2015 Science as an Explanatory Enterprise The difference between science and other enterprises that seek explanations of why things are the way they are can be found in the sorts of standards that science sets itself for what will count as an explanation, a good explanation, and a better explanation. (Alex Rosenberg) Inference to the Best Explanation Very often, scientists will adopt a theory because it would, if true, give us the best explanation for some confusing data we have. Example: Darwin’s theory is the first one to properly explain why the structure of life would take its familiar “groups-within-groups” form Counterexample: Lavoisier’s chemistry was worse at explaining lots of things than its predecessors Quick terminology explanans: The things that are doing the explaining (usually data and theories) explanandum: The thing that’s getting explained (the thing that we’re “dumb” about, not that that’s valid Latin etymology) The First Model: D-N The covering law theory of explanation (or the deductive-nomological theory): A good scientific explanation is a deductive (logical) argument with the explanans as its premises, invoking a law of nature, and the explanandum as its conclusion. Some Caveats 1 The explanation must be a valid deductive argument. 2 The explanans must contain at least one general law actually needed in the deduction. 3 The explanans must be empirically testable. 4 The sentences in the explanans must be true. Characteristics of the D-N Model • Explanation and prediction are basically the same. • Laws are really important. (And really difficult to explain.) • Statistical or probabilistic arguments (remember causation in lung cancer?) are hard to explain on this theory. The Big Problem Asymmetry in explanations Symptoms of diseases can’t explain the diseases. (Your illness isn’t explained by saying that you’re flushed and have a temperature of 103.) But symptoms of diseases can predict other symptoms of diseases, say. (If you have some very particular kind of fever, we can predict you’ll probably have some other symptoms A, B, and C, since you probably have disease X.) Explanations are asymmetric. And the D-N theory doesn’t say so, so it’s wrong. Unification An alternative: A good scientific explanation is one that explains a wide diversity of phenomena using a small set of basic premises and kinds of arguments. (That is, it unifies our understanding of a wide variety of natural phenomena.) Seems to work well for: Newtonian mechanics, evolution Doesn’t seem to work well for: chemistry Causation What about this theory: A good scientific explanation is a description of the causes of the phenomenon at issue. Trouble: Causation is really confusing! So this describes something confusing (explanation) in terms of something even more confusing (causation). Advantage: This does seem to be what lots of scientists are doing every day. Testing hypotheses about what things cause what other things by crafting specific kinds of experiments. Pluralism? Why not both? Pluralism Maybe we can craft a theory that holds that some kinds of explanations are used in some areas, and other kinds in others. Example, from Kuhn: At first, people thought that Newton hadn’t explained anything. But now, we think he did – because we think just giving a mathematical law can be an explanation. Pragmatism
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