To: Mark S.
From: Geoffrey Klempner
Subject: Karl Popper's response to Hume
Date: 15th November 2011 12:38

Dear Mark,

Thank you for your email of 6 November, with your essay for the University of London BA Methodology module, in response to the question, 'Does Popper provide an adequate response to Hume's problem of induction?'

You have taken this question as an invitation to discuss the merits of Popper's account of falsifiability as a descriptive and normative account of scientific practice.

As you have covered many of the main lines of criticism and defence, I was surprised you didn't mention the difficulty posed by existential statements, such as, 'There is an uncharged subatomic particle which has exactly one half the mass of a neutron' (I don't know whether this is true or not -- sounds false to me). This looks like a statement you could verify, at least by the standards of particle collision data (whose interpretation is of course heavily theory dependent) but it cannot be falsified.

Well, so what. A physicist wouldn't say this unless they had a theory which predicted it. A theory which only has positive existential claims like 'somewhere in the universe there is an uncharged particle with half the mass of a neutron' as its logical consequences is not scientific by Popper's criterion.

At one point in your essay you note that Popper is not seeking to show that induction is rationally justified. Of course not. His response is that the attempt to seek a rational justification for induction is just a wild goose chase.

However, the problem with this easy answer, which arguably should have been a focus of your essay, is that Hume makes precisely this claim. The 'problem' of induction for Hume is not something which he treats in the same way as the seemingly paradoxical conclusion (in 'On Scepticism With Regard to the Senses') that we cannot make sense of the assertion that objects which we do not perceive have a 'continued' and 'distinct' existence. (The only solution is to give up philosophy and take a rest from these 'strained speculations'.)

For Hume, the process of induction describes how beliefs are in fact formed. Moreover, there are 'rules for judging causes and effects', which themselves have arisen from the same source (habit), which allow us to 'reason' about alternative theories and decide which is 'best'. The point being that there is no standpoint or foundation from which we could judge the rationality of induction, or science, as a whole. It's just what we do.

Popper is right (in my view) to respond that Hume's account is to a considerable extent infected with the 'Baconian myth', but then Hume's interest was different. His 'rules' are elementary, hardly a philosophy of science or a methodology. You can read Popper as pointing out that there is something really interesting here, about how far actual scientific practice deviates from the mythical inductivist picture. With a bit of added hyperbole, maybe.

You are right to emphasize that the key question is why we rely on the results of science. But not all science, of course. There are the games cosmologists or particle physicists play, which seem to have little significance for the 'real' world. Not a lot different, in fact, from the games scholars of the Presocratics play, arguing the toss over different interpretations of Heraclitus. (Imagine you are a bemused bystander who in a misguided attempt to end the argument tries to formulate a 'philosophy of Presocratic interpretation'.)

However, at the back of the practical application of science lies our absolute, unremitting faith in the uniformity of nature. When you put questions to nature the answer will always be the truth, the whole truth and nothing but. It's up to us to put the right questions -- so often we fail to do this, or else lamely misinterpret the answers that nature gives. I don't see any merit at all in attempting to justify this faith or demonstrate its 'rationality' and neither did Hume.

If you asked Popper, what would he say? Is 'nature always tells the truth' also a falsifiable hypothesis, on the same level as all the rest? It's something we hold on faith, a presupposition of scientific inquiry. It seems to me perfectly acceptable to say that you don't judge the ultimate presuppositions of science by the standards of science. What an absurd idea!

Nitpicking objections apart, the great strength of Popper's vision lies in his realization that when we do science, there are always several theories 'on the table', some of which we like a lot, others which we don't like nearly so much but can't rule out. There are no logical or methodological rules for 'liking'. A lot depends on fashion, grant funding, etc. Which is not to say that anarchy rules, on the contrary (I've made his point before).

However, you don't build bridges on the basis of your favourite theory. That would be a rather silly thing to do. When it comes to bridges something else comes into play. What exactly is this? What response could Popper offer here other than the Humean response, which he apparently rejects? But does he, really?

To offer a 'conjecture and refutation' model for science (and maybe for Presocratic interpretation too -- see Popper's 'Back to the Presocratics') is not to claim that all human beliefs follow this pattern. If the presuppositions of science are not science, then neither are the basic beliefs which guide our everyday actions, Humean style, habits which we would never once think of questioning. This isn't necessarily an answer, or an adequate defence of Popper. He owes us an account of what it means to be a 'rational agent' at the basic, nitty gritty level. Corroboration looks like such an account. All Popper needs to do is swallow his pride and acknowledge his indebtedness to Hume.

All the best,

Geoffrey