 Wolff gives the following definition of philosophy in his German Logic: “[p]hilosophy is the science of all possible things, together with the manner and reason of their possibility” (Preface, §1). Now because of its subject matter, philosophy is considered by Wolff to be the broadest and most fundamental science. In the classification of sciences given in his Preliminary Discourse, Wolff first divides philosophy into two branches: practical philosophy, on one hand, and theoretical philosophy, on the other. Practical philosophy deals (in general) with human actions and includes morality, politics, jurisprudence, and economics. Theoretical philosophy, by contrast, deals with sets of possible and actual objects and is (itself) divided into three separate branches: (1) ontology, or metaphysics proper, (2) “special” metaphysics, which includes general cosmology, psychology and natural theology, and (3) physics (DP: §92). Whereas ontology and general cosmology are considered by Wolff to be completely “pure” (or a priori) sciences, psychology, natural theology, and physics are considered to be based upon empirical (i.e., historical) principles. As a brief aside, Wolff and the Critical Kant hold very different views on the relationship between practical and theoretical philosophy. Whereas Wolff believes that all of practical philosophy is subordinated to metaphysics (i.e., ontology as well as the three sub-disciplines that comprise special metaphysics), the Critical Kant argues for the independence of practical from theoretical principles. Wolff, in stark contrast, maintains that discoveries and conclusions made in practical philosophy are necessarily based upon prior conclusions drawn from ontology or metaphysics.