This chapter presents a selection from the notes (Reflexionen) that Erich Adickes edited under the title “Metaphysics” in volumes 17 and 18 of the Akademie edition, published in 1926 and 1928. This is by far the largest group of Kant's surviving notes, touching upon issues central to his works on theoretical philosophy through and beyond the second edition of the Critique of Pure Reason (1787) but also upon the metaphysical foundations of his practical philosophy and his moral theology, and thus this chapter is the largest of those in this volume. It is divided into four main parts, following the dates that Adickes provided for the notes: 1. Notes Prior to 1773; 2. Notes from 1773 to 1780, the crucial period for the composition of the Critique of Pure Reason; 3. Notes from the 1780s, including material from the period of the composition of the Prolegomena to any future metaphysics (1783) and the preparation of the second edition of the Critique; and 4. Notes from the 1790s, revealing Kant's continued thinking on some of the topics of the first Critique, especially his continued work on the “Refutation of Idealism” that he had added to the second edition. A small amount of material from volumes 17 and 18 is presented elsewhere in the present volume or the Cambridge edition: the first three reflections in volume 17, 3703 through 3705, were presented in conjunction with Kant's 1759 essay “On Optimism” in the volume Theoretical Philosophy, 1755–1770, translated and edited by David Walford in collaboration with Ralf Meerbote (Cambridge: Cambridge University Press, 1992), pp. 77–83, and several notes found among the notes on metaphysics but directly addressing topics in moral philosophy are included in Chapter 4 below.