What applies universally to all rational beings cannot be discovered through mere empirical experience, which is particular and contingent.

In Book II of the Groundwork (1785 [1996]) Kant claims the fundamental moral truths are synthetic a priori because moral truths are prescriptive. Kant held that the categorical imperative is not analytic, because although Kant thought the applicability of the categorical imperative to any given individual is deducible from the assumption that the individual is rational, the concept of the categorical imperative is not contained in the concept of a rational being. Kant thought the categorical imp