What in nature is the compulsion of reason?

If reason is a real causal force, operative in some, but not all of our cog nition and conation, then it ought to be possible to tell a naturalistic st ory that distinguishes the mind which is moved by reason from the mind whic h is moved by forces other than reason. This essay proposes some steps towa rd that end. I proceed by showing that it is possible to reconcile certain emerging psychological ideas about the causal powers of the mind/brain with a venerable philosophical vision of reason as the faculty of norms. My acc ount of reason is psychologistic, social, and consistent with an evolutiona ry approach to mind. The account preserves the normativity by deflating it. But I argue that only such deflated normativity has any chance of being ma de naturalistically respectable.