Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

This thinker observed that "every action can only take place in consequence of a sufficient motive" in The Basis of Morality, and also wrote an essay arguing that the title group of people can't take a "purely objective interest in anything", titled "On Women". This philosopher applied "observations of unbiased physical investigators" to the "kernel of [his] Metaphysics" in On the Will in Nature, and described four classes of objects in On the (*) Fourfold Root of the Principle of Sufficient Reason. The "Epistemology" volume of his best known work discusses the Kantian "thing-in- itself". For ten points, name this pessimistic German author of The World as Will and Representation.
Social Science