T 3.1.1.10

This argument is of double advantage to our present purpose. For it proves directly, that actions do not derive their merit from a conformity to reason, nor their blame from a contrariety to it; and it proves the same truth more indirectly, by shewing us, that as reason can never immediately prevent or produce any action by contradicting or approving of it, it cannot be the source of the distinction betwixt moral good and evil, which are found to have that influence. Actions may be laudable or blameable; but they cannot be reasonable or unreasonable: Laudable or blameable, therefore, are not the same with reasonable or unreasonable. The merit and demerit of actions frequently contradict, and sometimes controul our natural propensities. But reason has no such influence. Moral distinctions, therefore, are not the offspring of reason. Reason is wholly inactive, and can never be the source of so active a principle as conscience, or a sense of morals.