The categorical imperative is a fundamental moral law that applies to all rational beings universally.

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