Prolegomena to Any Future Metaphysics (1783)

In Prolegomena to Any Future Metaphysics, Kant primarily intended to clarify and simplify what was said in his Critique of Pure Reason, which was met mostly with bewilderment when it was first published in 1781. Readers generally failed to appreciate the originality of Kant’s ideas, including his belief that rationalist metaphysics—the main occupation of philosophers in Germany at the time—could be dismissed entirely, which proved to be too revolutionary a concept. In Prolegomena to Any Future Metaphysics, Kant reconceives the purpose of metaphysics as seeking to understand how knowledge is structured, and consequently how the various concepts of our mental faculties are organized. This was an important step for philosophy, since after Kant published his work there was been less interest in making broad claims about the nature of the universe and greater emphasis on determining what we can know and on what grounds we can claim to know it.

Grounding for the Metaphysics of Morals (1785)

In Grounding for the Metaphysics of Morals, Kant introduces many of the arguments that he would present more fully in his Critique of Practical Reason in 1788. “Metaphysics” is a field of philosopy focused on the study of pure concepts as they relate to moral or physical experience. Kant’s goal for Grounding for the Metaphysics of Morals was to develop a clearer understanding of moral principles, so that people may better avert distractions. Grounding for the Metaphysics of Morals represents a characteristic quality of Enlightenment era thinking: an immense confidence in “reason”—that is, in humanity's ability to solve problems through logical analysis. Kant’s philosophical goal was to use logical analysis to understand reason itself. Before we go about analyzing our world, Kant argued, we must understand the mental tools we will be using.

Critique of Practical Reason (1788)

Critique of Practical Reason presents Kant’s Doctrine of Elements, containing the Analytic of Pure Practical Reason and the Dialectic of Pure Practical Reason. The Analytic contains the arguments for the categorical imperative as the one true moral principle and for the identity of morality and freedom while the Dialectic exposes the primary error of all previous ethicists and proposes the postulates of pure practical reason. Critique of Practical Reason concludes with the Doctrine of Method, in which Kant proposes a new method for moral education.

Critique of Judgment (1790)

Kant’s Critique of Judgment, often called the “third critique,” does not have as clear a focus as the first two critiques. In broad outline, Kant sets about examining our faculty of judgment, which leads him down a number of divergent paths. While Critique of Judgment deals with matters related to science and teleology, it is most remembered for what Kant has to say about aesthetics. While much of what Kant writes about aesthetics might strike us now as a bit dated, his work is historically very significant. Kant’s “third critique” is one of the early works in the field of aesthetics and one of the most important treatises on the subject ever written.

Critique of Judgment is the subject of a single-section Summary & Analysis in the SparkNotes guide Selected Works of Immanuel Kant.