One of the greatest figures in the history of Metaphysics. After 1755 he taught at the Univ. of Knigsberg and achieved wide renown through his teachings and writings. According to Kant, his reading of Hume woke him from his dogmatic slumber and led him to become the "critical philosopher," synthesizing the rationalism of Leibniz and the skepticism of Hume. Kant proposed that objective reality is known only insofar as it conforms to the essential structure of the knowing mind. Only objects of experience, phenomena, may be known, whereas things lying beyond experience, noumena, are unknowable, even though in some cases we assume a priori knowledge of them. The existence of such unknowable "things-in-themselves" can be neither confirmed nor denied, nor can they be scientifically demonstrated. Therefore, as Kant showed in the Critique of Pure Reason (1781), the great problems of metaphysics-the existence of God, freedom, and immortality-are insoluble by scientific thought. Yet he went on to state in the Critique of Practical Reason (1788) that morality requires belief in their existence. Kant's Ethics centers in his categorical imperative, or absolute moral law, "Act as if the maxim from which you act were to become through your will a universal law." His Critique of Judgment (1790) considered the concepts of beauty and purposiveness as a bridge between the sensible and the intelligible worlds. Kant's influence on modern philosophy has continued to the present day. His work fostered the development of German idealism by Ficthe, Schelling, and Hegel. The Neo-Kantianism of the late 19th cent. applied his insights to the study of the physical sciences, and to the historical and cultural sciences; his influence is also seen in Gestalt psychology.