The Critique of Pure Reason

[QandC]

Immanuel Kant was a freaking genius: 

https://www.gutenberg.org/files/4280/4280-h/4280-h.htm#chap12

[Reciprocality]

@QandC For transcendental entities or principles to be meaningful things or existence must first be considered as contingent or "could have not been", such principles were traditionally the laws of logic, sufficient reason and parsimony but with Kant it became the most primitive accidents that are necessary for every thing to appear and therewith entirely inessential for the identity of each one thing, and so it was that space and time became the conditions for the possibility of experience in Kants view.

Unfortunately he never demonstrated that the directly present experience in existence is contingent, it could very well be that the necessary accidents such as the concepts of time and space are the contingent variable which humans naturally abstract or identify from the relation between things in motion, just as humans construe the "possible" from decoupling representation from the presented.