Schopenhauer in his key philosophical work The World as Will and Representation, reacts against the supremacy of human’s reason and intellect by assuming a force that underlies the reason itself, hidden as a deep foundation that allows and explains human actions. He accepts that the ultimate and irrational reality is a blind and involuntary force called the Will. This underlying force manifests itself in the human body while the intellect or rationality is just an instrument that holds back, up to a certain point, the irrational desires of this essential force. The main purpose of this article is to trace, inside of the philosophy of Schopenhauer, a theory of the way human mind works, as well as a theory of the irrational drives, of repression and madness based on the acceptance of his irrational will.