Zinkin (2006) explains the free play in terms of the sensus communis invoked by Kant at §20, which she understands as an intensive form of sensibility, in contrast to the extensive forms of sensibility represented by space and time.
For the organic conception of rationality that that theory implied — reason being nothing more than a more developed, more reflective, form of sensibility — fitted well indeed with Leibniz's system.
Although in the last kind of proposition the meaning of the predicate term is not contained in the meaning of the subject term, it is nevertheless possible to know the proposition independently of experience, because it expresses a condition imposed by the forms of sensibility.
Thought implies an ability to experience representations of another type not involving the forms of sensibility — space, time, and causality.
The first, the phenomenal realm, consists of appearances or objects of possible experience, configured by the forms of sensibility and the epistemic categories.
In particular, his doctrine of space and time as forms of sensibility was given a naturalistic construal in the physiology and psychology of perception.
The second level of the a priori consists in the forms of sensibility and the understanding, that is, space, time, and the categories.
But the necessity of these forms ultimately derives from the necessity of the third level of the a priori, because the forms of sensibility and understanding are "scientific abstractions" (Cohen 1987 [1871b], 83 84) from that third level.
To assume this is to take what are for Kant merely subjective features of our intuition (forms of sensibility, space and time) to be universal ontological conditions holding of everything whatsoever.
The central arguments of this digression, which comes in Herz's exposition of Kant's new theory of space and time as the forms of sensibility, are first, that beauty is an objective property especially connected to the form of an object, and not a mere sensation or sentiment (Empfindung) in the subject, and second, that there are general principles of beautiful form.
Of course, this revisionist tendency greatly transformed the meaning of Kant's Transcendental Aesthetic and with it Kant's conviction that space and time were forms of sensibility or pure intuitions a priori and so as well, his accounts of arithmetic and geometry.
