 Kant had just completed the latter task, in fact, in his Metaphysical Foundations of Natural Science, which had meanwhile appeared in 1786 (following the publication of the Prolegomena in 1783 and immediately preceding the publication of the second edition of the Critique in 1787). There Kant articulates what he calls “pure natural science” in four chapters corresponding, respectively, to the four headings of the table of categories (quantity, quality, relation, and modality). In the third chapter or Mechanics (corresponding to the three categories of relation: substance, causality, and community) Kant derives three “laws of mechanics” corresponding, respectively, to the three Analogies of Experience: the permanence or conservation of the total quantity of matter, the law of inertia, and the equality of action and reaction—which Kant describes as a law of “the communication of motion” (4, 544; 84). All these laws, Kant makes clear, are synthetic a priori propositions, demonstrated a priori and “drawn from the essence of the thinking faculty itself” (4, 472; 8).