Chapter 3 turns to the fundamental metaphysical concept in Kant, the concept of the ‘really’ (not just logically) unconditioned, and to the conditioning relations between objects that speculative metaphysics tracks. Kant’s Rational Sources Account (his argument that the sources of speculative metaphysics lie in reason itself) rests on the claim that the logical use of reason naturally leads us to accept a principle he calls the “supreme principle of pure reason.” In this chapter, we will try to clarify this principle by asking what Kant, in the context of the Supreme Principle, means by ‘given,’ by ‘the conditioned’ and its ‘conditions,’ what it means for something to be ‘unconditioned,’ and why Kant thinks the series of subordinated conditions is supposed to be unconditioned in this sense. Finally, we will ask how that principle relates to the Principle of Sufficient Reason.

The Introduction explains the two major aims of the book. First, the book will offer a novel interpretation of the Transcendental Dialectic that isolates its constructive side, Kant’s account of the rational sources of speculative metaphysics (concerning the soul, the world as a whole, and God), and distinguishes it clearly from its destructive side, Kant’s critique of this kind of metaphysics. Second, it will reconstruct, and where possible defend, a Kantian account of the rational sources of metaphysical thinking. In particular, it will argue that Kant is right in claiming that metaphysical speculation arises naturally out of principles that guide us in everyday rational thought. As the book will argue, Kant gives us good reason to think that discursivity, iteration, and striving for completeness are fundamental features of rational thinking and that, taken together, they give rise to a specific kind of metaphysical speculation. This is a distinctive and original perspective on metaphysics that deserves to be taken seriously in the current metaphysical and meta-metaphysical debates.