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The Most Important Improvement to Popperian Philosophy of Science

Here is (my summary, my words) the most important idea contributed to Popper's philosophy of science by someone other than Popper. It was contributed by David Deutsch in his book The Fabric of Reality:

Most ideas are criticized and rejected for being bad explanations. This is true even in science where they could be tested. Even most proposed scientific ideas are rejected, without testing, for being bad explanations.

Although tests are valuable, Popper's over-emphasis on testing mischaracterizes science and sets it further apart from philosophy than need be. In both science and abstract philosophy, most criticism revolves around good and bad explanations. It's largely the same epistemology. The possibility of empirical testing in science is a nice bonus, not a necessary part of creating knowledge.

In his book, David Deutsch gives this example: Consider the theory that eating grass cures colds. He says we can reject this theory without testing it.

He's right, isn't he? Should we hire a bunch of sick college students to eat grass? That would be silly. There is no explanation of how grass cures colds, so nothing worth testing. (Non-explanation is a common type of bad explanation!)

Narrow focus on testing -- especially as a substitute for support/justification -- is one of the major ways of misunderstanding Popperian philosophy. Deutsch's improvement shows how its importance is overrated and, besides being true, is better in keeping with the fallibilist spirit of Popper's thought (we don't need something "harder" or "more sciency" or whatever than critical argument!).

Emphasis on explanations is a theme with Deutsch. His upcoming book, The Beginning of Infinity is subtitled "Explanations that transform the world".

Another big idea of Deutsch's is that Popperian epistemology is true for all people. It sounds obvious when stated in that form, but it becomes controversial when one mentions that children are included in "all people". I think Popper would have approved of this, but he didn't go through and explain the consequences and implications for education. Deutsch has done so in detail.


In An Introduction To The Thought Of Karl Popper, p 41, Roberta Corvi summarizes Popper, "The practical problem of induction is thereby solved: it is transformed into the problem of testing a theory". This is just the kind of empiricist mistake which Deutsch has improved on. Empirical approaches are insufficient in general because they cannot address philosophy (and epistemology should apply to all knowledge), but even in science when testing is possible, strong empiricism (i.e. we learn primarily using observation) is still a mistake.

Elliot Temple on August 20, 2010

Comments (5)

Interesting, but what is the difference between a conjecture and an explanation. Didn't Popper move away from this emphasis on testing, to problems and how to solve them. It seems to me that explanations are a part of Poppers philosophy before Deutsch. Though I might be wrong, because one of my first forwys into Popperianism was Deutsch's book, and so I always thought that was a core part of Popper's philosophy.

Andrew Crawshaw at 10:26 PM on January 15, 2015 | #2413 | reply | quote

The Arbitrary

This seems like a straight up application of the Objectivist idea of the arbitrary. That is, if an idea has absolutely nothing going for it (the moon is made out of cheese!) it should be rejected out of hand without even being considered possible.

And I believe the lesswrongians later popularized an annoyingly named version of this idea as well, ”not even wrong”.

JN at 9:24 PM on May 10, 2019 | #12323 | reply | quote

No, it's about criticizing some actual flaw in something. Not that it's "arbitrary" but something is actually wrong with it. The point is most flaws are not "contradicts the evidence". There are other types of flaws which are used all the time.

Rejecting things for being "arbitrary" is a way of rejecting ideas *which may be true*, without thinking about them. It's deeply irrational. Rejecting ideas "out of hand" and "without ... being considered ..." is *bad* – that's a refusal to think.

Dagny at 9:27 PM on May 10, 2019 | #12324 | reply | quote

bad is not just arbitrary

#12323 Let's take the idea that the moon is made of cheese seriously for a moment. If that idea is true, then the cheese should affect light reflected off the moon from the sun. The effects of cheese reflecting light are different from those of rock reflecting light. So we would be able to detect those effects and we don't.

In addition, people have been on the moon and have reported rock and dust, not cheese.

The problem with saying the moon is made of cheese isn't that it has nothing going for it, but that there are lots of criticisms of it and no answers to those criticisms.

oh my god it's turpentine at 4:57 AM on May 11, 2019 | #12328 | reply | quote


> But experimental testing is by no means the only process involved in the growth of scientific knowledge. The overwhelming majority of theories are rejected because they contain bad explanations, not because they fail experimental tests. We reject them without ever bothering to test them. For example, consider the theory that eating a kilogram of grass is a cure for the common cold. That theory makes experimentally testable predictions: if people tried the grass cure and found it ineffective, the theory would be proved false. But it has never been tested and probably never will be, because it contains no explanation — either of how the cure would work, or of anything else. We rightly presume it to be false. There are always infinitely many possible theories of that sort, compatible with existing observations and making new predictions, so we could never have the time or resources to test them all. What we test are new theories that seem to show promise of explaining things better than the prevailing ones do.

Anonymous at 6:13 PM on November 7, 2019 | #14229 | reply | quote

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