  Ordinary cognition, according to Schopenhauer, is bound up with the individual’s will, that is to say, with one’s generally egoistic strivings, and is subordinate to the four forms of the “principle of sufficient reason” (PSR), the principle which holds that nothing is without a reason for why it is (FR, §5). The PSR is Schopenhauer’s formulation of the ways in which human beings cognitively condition the world of representation. It includes space, time and causality, as well as psychological, logical and mathematical forms of explanation. 