In this chapter, the metaphysics of quantum possibilities, as a form of res potentia, is discussed. The transactional picture, together with quantum possibility, can be understood in terms of Kant’s contrast between phenomena and noumena, with quantum possibility constituting an element of the noumenal realm. This formulation sheds light on the connection between the two realms. It also provides a “middle way” between realism and antirealism and resolves puzzles surrounding the notion of causation. Concerns about structural realism are also addressed.

Chapter 4 seeks to resolve the apparent contradictions in Kant's account of the thing in itself and related terms by interpreting the relevant passages in light of his critique of Wolffian metaphysics. The chapter departs from both the two-aspect view defended by Allison and the two-object view that Guyer attributes to Kant. Moving beyond this opposition, the chapter dissociates Kant’s remarks on the objects that affect our senses from his use of the term ‘thing in itself’ and its cognates in the context of his critique of Wolffian and post-Wolffian metaphysics. In the latter context, it is argued, the term refers to things that can be thought but cannot constitute objects of cognition. The chapter shows that Kant’s account of the thing in itself in this sense and, hence, the distinction between phenomena and noumena allows him at once to limit the scope of former ontology to possible objects of experience and to affirm the ideas of the soul, the world as such, and God as noumena that can be thought but not known.