The World as Will and Idea: 3 volumes in 1 [unabridged]

Schopenhauer believed that Kant had ignored inner experience, as intuited through the will, which was the most important form of experience. Schopenhauer saw the human will as our one window to the world behind the representation; the Kantian thing-in-itself. He believed, therefore, that we could gain knowledge about the thing-in-itself, something Kant said was impossible, since the rest of the relationship between representation and thing-in-itself could be understood by analogy to the relationship between human will and human body. According to Schopenhauer, the entire world is the representation of a single Will, of which our individual wills are phenomena. In this way, Schopenhauer's metaphysics go beyond the limits that Kant had set, but do not go so far as the rationalist system-builders who preceded Kant.