The basic presupposition shared by Heidegger and other philosophers in the rational-metaphysical tradition from Plato and Aristotle onwards is that the central metaphysical question is a Why-question, and is about the reason or reasons that explain why everything is and is as it is. Metaphysicians from Plato to Hegel presupposed the most fundamental metaphysical truth to be the answer to this question, and metaphysicians from Schopenhauer onwards presupposed the most basic metaphysical truth to be the unanswerability of this question.

Quentin Smith, The Felt Meanings of the World: A Metaphysics of Feeling, West Lafayette, Indiana, 1986, p. 13