In many contexts, simplicity is not an aesthetic frill.

I think that some "interventionist theisms" are compatible with evolutionary theory. (By "intervention," I don't mean that God violates laws of nature; I mean that God affects what happens in nature in ways that are additional to the ones that deism recognizes.)

In many contexts, simplicity is not an aesthetic frill.

Earlier attempts to show that simpler theories always have higher prior probabilities have failed, but there is a restricted circumstance in which the claim is right.

Trait X is fitter than trait Y in a population of organisms if those organisms have other biological traits T and live in an environment that has properties E. The theory of natural selection is filled with statements of this form.

Darwin repeatedly used the hypothesis of common ancestry as a platform on which to build his various ideas about testing hypotheses concerning natural selection. He also argued that adaptive similarities provide little or no evidence for common ancestry. Although this second claim needs to be fine-tuned, Darwin was right that ample evidence for common ancestry can exist even if none of the characteristics we observe were caused to evolve by natural selection.

If you have evidence that C1 is a cause of E, and no evidence as to whether C2 is also a cause of E, then C1 seems to be a better explanation of E than C1&C2 is, since C1 is more parsimonious. I call the version of Ockham's razor used here "the razor of silence." The better explanation of E is silent about C2; it does not deny that C2 was a cause. The problem changes if you consider two conjunctive hypotheses.