Or, why empiricism isn’t as crazy as Hume thought
Awhile back I promised a post on “scientism”–a popular target of religious apologists, though it’s not always clear what it’s supposed to be. Before I discuss it, though, I want to discuss a more philosophically respectable idea, empiricism, and the very philosophically respectable objection to it: that it cannot serve the problem of induction.
(1) Empiricism: The doctrine that outside a special class of conceptual truths, which are true in virtue of how the concepts involved are defined, all human knowledge depends on evidence and observation
(2) Induction: The process of inferring general facts about the world from many specific facts. For example, inferring “the sun rises every day” from “the sun rose today, yesterday, two days ago, three days ago…” or inferring “everything orbiting the Sun follows Kepler’s laws” from “Mercurey, Venus, Earth, and Mars follow Kepler’s laws.
(3) Problem of Induction: In the words of the SEP, the question of “can induction be justified?”
David Hume, possibly the most famous empiricist ever (though he’s got competition from John Locke), thought that because empiricism is true, induction can’t be justified, and since induction can’t be justified, we can’t know things like “the sun rises every day,” and the therefore we can’t know things like “the sun will rise tomorrow.” Other philosophers, such as Laurence Bonjour, have reversed the argument: if empiricism were true we couldn’t know that the sun will rise tomorrow, but plainly we can know this, so empiricism is false.
For a year or two of my undergraduate career, I thought this argument was totally conclusive, and wondered why everyone didn’t accept it. But why think induction couldn’t be justified if empiricism were true? Hume put it this way: “all inferences from experience suppose, as their foundation, that the future will resemble the past.” This is no conceptual truth, since we can conceive of the future bearing no resemblance to the past. But it can’t be known by experience, either: “It is impossible that any arguments from experience can prove this resemblance of the past to the future; since all these arguments are founded on the supposition of that resemblance.” To prove “this resemblance” by experience, then would be circular reasoning.
Richard Chappell has endorsed an argument somewhat like this, but ironically, I credit Richard with persuading me that the argument is a bad one. The trouble is this: not all elements of an inference are on equal footing, something Richard has pointed out with respect to intuitions and pesuppositions. In the case of intuitions: lots of philosophers are convinced that no chain of reasoning can get started without accepting that some things are just obvious or “known by intuition,” but that doesn’t mean that the obviousness of an argument’s premises is itself a premise. Similarly, to mathematical theorem means assuming that, at each step, you can accurately remember what you did in the previous parts of the deduction, but that doesn’t make “my memory is reliable” an important mathematical axiom.
Similarly with induction. Suppose there is a Principle of Justified Induction that says “under such-and-such circumstances, being justified in believing that a generalization holds for many cases justifies believing that the generalization holds for all cases,” and that principle is true. If such a principle were true, then inferring “the sun rises every day” from “the sun rose today, yesterday, two days ago, three days ago…” would, under the such-and-such conditions, be a good inference, and the Principle of Justified Induction would not play the same role in the inference as the belief that “the sun rose today” played. Neither would Hume’s statement that “the future will resemble the past.” The trouble is that normally, it’s beliefs that need justification, while induction is a process, and expecting a process to be justified the way a belief is is a recipe for a headache.
If this isn’t obvious, I suggest reading Lewis Carroll’s short story “What the Tortoise Said to Achilles,” which makes the same point about deduction. Were Hume’s criticism of deduction legitimate, we could also conjure up a “problem of deduction” by claiming that all deductions rely on the supposition that deductive inferences work, and then ask where that supposition comes from.
Interesting corollary: if I’m right about all this, the seemingly odd suggestion that we can inductively justify induction is half-right. It’s not that we really can do this, but that we can inductively justify beliefs about induction. Since beliefs about induction are not part of inductive inferences the way instances of the generalization to be justified are, there’s no risk of circularity at least in the ordinary sense of the word.
Obligatory paradoxical epilogue: I’m sure I’ve missed something here. Any philosophy nerds reading this (Richard? You reading this?) please tell me what it is.