The Beginning of Infinity

Two explanations of why the earth goes cold for part of every year. One is Persephone, held below for a third of it while her mother grieves and the grieving earth cools. One is a planet leaning 23.4° out of the plane of its orbit. In ancient Greece both fitted every observation anybody had, and no evidence could separate them — because a bad explanation can be adjusted to fit anything at all. What separates them is structural, and you can check it from a chair without measuring a thing: how much of the explanation could you change and have it still explain the thing? The myth survives every change you can make to it. The tilt survives almost none. Deutsch builds a whole epistemology on that asymmetry, and it reaches a great deal further than it has any right to.

A reading of David Deutsch's The Beginning of Infinity: Explanations That Transform the World (Viking, 2011): the hard-to-vary criterion and why evidence alone cannot separate a good explanation from a myth, the claim that observation has never once generated a theory, the unearned reach of explanations that turn out to be about something real, the discrete jump to universality, the inversion of Spaceship Earth, static societies and the ideas that survive by disabling criticism, and the difference between optimism and prophecy — with three working instruments, one of which audits a belief the reader brings to it.