In his main work, The World as Will and Representation, first published in 1819, Schopenhauer presents his philosophy in a comprehensive and systematic manner. In the first two of the four total "books" of the work, those included in the first volume of the Greek edition at hand, he initially deals with the object, the constitution, and the limits of human knowledge (Book I), and then with the essence of beings, the essence of reality itself (Book II). Human knowledge is determined by the a priori forms of the cognitive mechanism of the subject and is conducted initially at the level of intuition and subsequently at the level of abstract knowledge. Access to the essence of beings is provided by the direct inner experience of the will, which constitutes the metaphysical essence of reality.

The World as Will and Representation is undoubtedly one of the great classic works of European philosophy, with a significant influence on all fields of human thought. It incorporates a large part of the previous philosophical tradition and itself serves, both directly and indirectly, as a very important source of modern philosophy.