Modern Philosophy: From the Post-Kantian Idealists to Marx, Kierkegaard, and Nietzsche

Abstract

The development of German philosophy in the nineteenth century begins with the radical transformation of Kantian criticism into absolute idealism. By eliminating the “thing-in-itself,” the systems of Fichte, Schelling, and Hegel characterize reality as a unified, teleological process of self-manifesting Reason or Spirit. This speculative peak is succeeded by diverse reactions that prioritize the concrete over the abstract. Schopenhauer counters rationalist optimism with a metaphysical voluntarism centered on an irrational Will to live. Concurrently, the Hegelian school bifurcates, leading to the transformation of theology into anthropology and the rise of dialectical materialism. In this context, the economic substructure replaces the logical Idea as the engine of historical progress. Parallel to this, Kierkegaard offers a religious critique of systematic thought, emphasizing individual choice and subjective existence over the universal. The century concludes with a dual movement: the Neo-Kantian return to epistemological limits and the emergence of Nietzsche’s radical perspectivism. Nietzsche’s rejection of absolute truth and the assertion of the Will to Power mark the final dissolution of the post-Kantian idealist framework. Collectively, these shifts demonstrate an intellectual transition from the mastery of speculative reason to a focus on the biological, social, and existential determinants of human life. – AI-generated abstract.