 Undoubtedly the central concept in Feuerbach’s last works, which include the essay, “On Spiritualism and Materialism, Especially in Relation to the Freedom of the Will”, and an incomplete essay on ethics, is the concept of the Glückseligkeitstieb or drive-to-happiness. Toward the end of the Preliminary Theses, after affirming that all science must be grounded in nature, and that doctrines not so grounded remain purely “hypothetical”, Feuerbach had gone on to note that this is especially true of the doctrine of freedom, and he had assigned to the new philosophy the task of “naturalizing freedom” (VT 262/172). This is one of the tasks to which he applies himself in “On Spiritualism and Materialism”, where he takes aim at “supernaturalistic” philosophers, among whom he counts Kant, Fichte and Hegel, who ascribe to human beings a noumenal or universal will that is “independent of all natural laws and natural causes and thus of all sensuous motivations [Triebfedern]” (SM 54). In arguing that it is possible for the will to be determined by the mere form of the moral law, independently of any sensible inclination, Kant had identified the will with pure practical reason. In doing so, Feuerbach argues, he turned the will into a mere abstraction. For Feuerbach it makes no sense to speak of a timeless will devoid of affect directed toward some particular object.