 By far the most original and influential portion of the Elementary Philosophy is its first part, the Theory of Representation, which is devoted entirely to an analysis of our fundamental faculty of the mind—the faculty of representation itself [Vorstellungsvermögen]—in an effort to determine “everything that can be known a priori concerning the representations of sensibility, understanding, and reason.” This foundational portion of the Elementary Philosophy thus purports to provide a thorough and complete analysis of the necessary features of representation qua representation, an analysis that claims to show “that space, time, the twelve categories, and the three forms of the ideas are originally nothing but properties of mere representations” (Fundament, pp. 72–73; RGS 4, 47). This same analysis of our faculty of representation also claims to establish the distinction between the form and content of representations, the necessity of both receptivity and spontaneity on the part of the faculty of representation, the necessary multiplicity of sensations, and the unknowability of things in themselves.