Discussion of the simplicity of hypotheses has advanced little since Mersenne. Everyone agrees that the simplicity of a scientific theory is a reason to believe it (or at least to “accept” it, in the jargon of the century of noncommitment). But why should it be? Does a theory’s simplicity make it more probable? If so, why? If not, why does it constitute a reason for preferring the theory? Newton’s “Nature is pleased with simplicity, and affects not the pomp of superfluous causes” is magisterial but unsupported by reasons.96 God may have the potential to be “pleased” with simplicity, but why
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