One of the basic concepts of the metaphysics of the pre-critical Kant is the early modern, Leibnizian concept of the world as a synthetic whole of simple substances. Space is the order according to which these simple substances coexist, in the presence of God. Kant’s turn to critical philosophy contained a re-evaluation of Leibnizian metaphysics. Space is an ideal form of sensibility, not a real order of coexisting simple substances. This dissertation argues that Kant’s critical turn inspired him to outline a new science of subjective space – the Transcendental Aesthetic.

Leibnizians argued that our knowledge of space is innate, but still abstracted from the common sense idea of extension. In the Critique of Pure Reason Kant responded that this misrepresents our knowledge of the subjective space, which is the topic of the Transcendental Aesthetic. An exposition of the marks of the concept of subjective space not only shows that space is a form of sensibility, but that it is a continuous, actually infinite whole, which precedes its potentially infinite parts. In Kant’s terminology space is an analytic whole, which gives a key to the ideality of space, according to this dissertation.

One important topic in the literature concerns Kant’s awareness of the Leibnizian alternative that space might be both a form of sensibility and an order of coexistence. This dissertation claims that Kant could not rule out this alternative completely. However, in one aspect, Kant was successful: Leibnizians had to admit that continuity belongs to space, not as an order of coexistence, but as a form of sensibility. We see all things in continuous space, not in God. However, seeing things in space is analogous to seeing them in God.