Reason is the source of transcendent principles. These principles are concocted by reason in its effort to unify the principles of the understanding by completing them. They employ Ideas, concepts whose intended objects are, as it were, free-standing, and which provide a foundation for the objects of experience. The basis of Wolff's division was this. Psychology's object is the soul, which is a special kind of contingent being.
Cosmology concerns the world, which is the aggregation of all contingent beings which exist.
Kant's systematization of the three areas of special metaphysics follows a three-fold division of types of syllogism in Aristotelian logic. The categorical, hypothetical and disjunctive syllogisms correspond to the doctrines of the soul, the world and God, respectively. This division is universally condemned as being so artificial as to be useless. The Paralogisms The Idea of the soul is that of a single simple substance in commerce with a body. In the first edition, this yields a division of the Paralogisms into four.