This is the basic starting point of all philosophical viewpoints, and it is also the fundamental standard for dividing philosophical factions (idealism/materialism). 2) The representatives are Kant, Fichte, Schelling, Hegel and Feuerbach. German classical philosophy is an important historical stage in the development of western philosophy. It has gone through two stages of development from idealism to materialism. 3) Kant is the founder of German classical philosophy. He established a philosophical system and agnosticism, which is essentially transcendental idealism, to reconcile contradictions. 4) Fichte inherited and criticized Kant from the standpoint of idealism and established a thorough philosophy of subjective idealism. 5) Schelling transformed Fichte's subjective idealism and established the same objective idealism philosophy. 6) Kiel is a master of German classical idealism. On the basis of criticizing and inheriting predecessors, he created a huge system of objective idealism. 7) Starting from humanism, Feuerbach criticized religious theology and Hegel's idealism, materialistically solved the basic problems of philosophy and founded humanistic materialism. The greatest achievement of German classical idealism philosophy is idealism dialectics. Kant affirmed the significance of human psychological structure and intellectual field, saw the dynamic role of cognitive subject, and revealed the inevitability of contradictions in rational thinking. 8) Fichte reveals the dialectical relationship between self and non-self, subject and object. In the stipulation that "self" is both the subject of cognition and the subject of action, he abstractly expounded the dynamic role of spirit and the dialectical unity of theory and practice. Schelling described the unity of opposites between self and non-self, subject and object more clearly, which made a more direct ideological preparation for the emergence of Hegel's dialectics. Geer systematically developed the epistemology and dialectics thought in Kant, Fichte and Schelling's philosophy, comprehensively expounded the main contents of dialectics, and promoted it to objective truth and universal law. Geer applied the concept of development to human society and revealed some historical dialectics, so in his philosophy, 9) However, the epistemology and dialectics in German classical philosophy are based on idealism, so they are unscientific and incomplete. The profound contradiction between this system and method is a reflection of the class character of the German bourgeoisie, which wants both revolution and actual struggle, and opposes feudalism and compromises with feudal forces. The development of German classical philosophy from Kant to Hegel and Feuerbach is a logical process and an inevitable product of German social relations at that time. It led the bourgeois political revolution in Germany from 65438 to 0848. 10) Marx and Engels critically transformed German classical philosophy, especially the philosophy of Hegel and Feuerbach, critically inherited the rational core of Hegel's dialectics and the basic core of Feuerbach's materialism, and founded Marxist philosophy. German classical philosophy is the theoretical source of Marxist philosophy.