Taking Popper Too Far, Again

I’ve written before that some fans of David Deutsch take Karl Popper too far.

Popper says we’re fallible: we eventually make mistakes somewhere. Deutsch’s fans, and Deutsch himself, say we always make mistakes everywhere; that “all human knowledge is false.” (2:51) That’s not the same thing.

There are two more areas where they take Popper too far: in their opposition to methods and to justification.

First, Popper stresses that there’s no Scientific Method™. He writes in Objective Knowledge (OK, 1979, p. 265):

If anyone should think of scientific method as a way which leads to success in science, he will be disappointed. There is no royal road to success.

He also writes:

Should anybody think of scientific method, or of The Scientific Method, as a way of justifying scientific results, he will also be disappointed. A scientific result cannot be justified. It can only be criticized, and tested. And no more can be said in its favour than that it seems, after all this criticism and testing, better, more interesting, more powerful, more promising, and a better approximation to truth, than its competitors.

Science depends on creativity, ingenuity, and imagination, and those depend in part on luck. So there’s no Method to science except the critical ‘method’. There’s no way to reliably generate true theories or to justify them.

But fans of Deutsch hear this and seem to mentally file away any kind of method as un-Popperian. It’s like they’re allergic to the word ‘method’ in general. So when I suggest that we can have a method to form rational preferences, they instinctively reject it because I use that word.

But my method also depends in part on luck; it doesn’t depend on fixed criteria; it doesn’t claim to be a royal road to success. It’s totally compatible with Popperian epistemology. In fact, it follows from it.

Also, what do they think Popper’s concepts of corroboration and verisimilitude (“better approximation to truth”) are for? Popper says we should prefer theories that are better corroborated and closer to the truth. Corroboration and verisimilitude are his ‘methods’ of preference.

Rationality depends on preference formation. Instead of calling it a ‘method’, we could call it a ‘principle’. Popper asks (OK p. 13):

The theoretician… is essentially interested in truth, and especially in finding true theories. But when he has fully digested the fact that we can never justify empirically—that is, by test statements—the claim that a scientific theory is true, and that we are therefore at best always faced with the question of preferring, tentatively, some guesses to others, then he may consider, from the point of view of a seeker for true theories, the questions: What principles of preference should we adopt? Are some theories ‘better’ than others?

He then says the “the question of preference will arise … with respect to a set of competing theories; that is, theories which are offered as solutions to the same problems.”

In other words, given a set of ideas, how do we rationally prefer one over the others? That’s the key question, a question that has puzzled philosophers since antiquity. Different epistemological schools have different answers. Inductivists, for example, say we should increase our credence for ideas when they match repeated observations. This is the context where Deutsch offers his own ‘method’ or principle: that of preferring the idea that’s “harder to vary” (HTV) while still explaining what it claims to explain.

But some Deutschians, in their opposition to ‘method’, claim that he did no such thing; that HTV is just a description of what happens to theories as they get better. What they don’t seem to realize is that this claim is actually a disservice to Deutsch, because it demotes his proposed solution to a central philosophical problem down to a mere observation about theories.

If the word ‘principle’ satisfies Deutschians, then I’ll happily drop the word ‘method’ in discussions with them. It’s no big deal. Just note that it still refers to the same underlying concept. For what it’s worth, Popper does not share their disdain for the word ‘method’. For example, he refers to “one of [his] principal methods of approach…” (OK p. 6). And throughout OK, he speaks of the “critical method” of science and uses the word ‘method’ over and over in various contexts.

Worse, I worry that the Deutschians’ disdain for the word ‘method’ has gotten so entrenched that they’ll dismiss any rigorous thought. That would be even worse for Deutschian epistemology than their demotion of HTV, because it would reduce it to vibes – in short, mysticism. One would have to choose one’s fans carefully, if it were possible.

So much for the issue of ‘method’.

Second, as we see in the quotes above, Popper stresses that we can’t justify theories. (More precisely, as he writes, we can’t justify the claim that a theory is true.) Here, Popper’s answer is the same as Hume’s: “no number of true test statements would justify the claim that an explanatory universal theory is true.” (OK p. 7)

Once again, Deutsch fans seem to have mentally filed away the word ‘justification’ as something to avoid in general; as something that’s impossible always and everywhere.

They seem to think that’s Popper’s stance. It isn’t. For one, Popper says “the assumption of the truth of test statements sometimes allows us to justify the claim that an explanatory universal theory is false.” For two, Popper says we can justify our preference for one idea over another (p. 8):

Can a preference, with respect to truth or falsity, for some competing universal theories over others ever be justified by such ‘empirical reasons’?
In the light of [the possibility of the justification of a falsity claim] the answer … becomes obvious: Yes; sometimes it can, if we are lucky. For it may happen that our test statements may refute some—but not all—of the competing theories; and since we are searching for a true theory, we shall prefer those whose falsity has not been established.

In short, Popper does not share this allergy to the word ‘justification’ that some of Deutsch’s fans seem to have. Popperian epistemology does not entail rejecting all justification, as they seem to think. Nor does it entail a rejection of all method or, worse, of all rigorous thought.