The Critique Of Practical Reason by Immanuel Kant

A foundational defense of moral philosophy arguing that practical reason, not contingent desires, grounds a universal moral law expressed as the categorical imperative; it emphasizes the autonomy and duty of rational agents, insists that freedom is a necessary presupposition of moral responsibility, and introduces postulates (such as God and the immortality of the soul) as practical necessities for realizing the highest good, while distinguishing the limits and authority of practical versus theoretical reason.

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