 In both the Preamble to the Prolegomena to Any Future Metaphysics and the B-Introduction to the Critique of Pure Reason, Kant introduces the analytic/synthetic distinction, which distinguishes between judgments the predicates of which belong to or are contained in the subject concept and judgments the predicates of which are connected to but go beyond the subject concept, respectively. In each text, he follows his presentation of this distinction with a discussion of his claim that all mathematical judgments are synthetic and a  priori.[4]  There he claims, first, that “properly mathematical judgments are always a priori judgments” on the grounds that they are necessary, and so cannot be derived from experience (B14). He follows this with an explanation of how such non-empirical judgments can yet be synthetic, that is, how they can serve to synthesize a subject and predicate concept rather than merely explicate or analyze a subject concept into its constituent logical parts.