Schopenhauer and knowledge

John Vespasian explains that, in his early years, Schopenhauer had declared allegiance to the epistemological doctrines of Immanuel Kant (1724-1804). I am referring to the theory of concept formation presented by Kant in his book “Critique of pure reason” (1781). In 1808, Schopenhauer published his PhD dissertation “On the fourfold root of the principle of sufficient reason,” stating his overall allegiance to Kant’s epistemology. However, there is one point where he had not endorsed Kant. On that point, Schopenhauer claimed that he was improving Kant’s epistemology, although in reality, he was nullifying one of the pillars of Kant’s “Critique of pure reason.” What was the point of discord between Schopenhauer and Kant? What drove Schopenhauer to build a new philosophical system almost from scratch? Schopenhauer diverged from Kant on the nature of “things-in-themselves” or “noumena.” Those Kantian terms refer to the ultimate reality behind appearances. Kant had employed the word “noumena” to refer to truths, ideas, concepts and principles that aren’t directly derived from perception. Here is the link to the original article: https://johnvespasian.com/schopenhauer-and-knowledge/