The answer to question one is broadly found in the Transcendental Aesthetic, and the doctrine of the transcendental ideality of space and time. In answer to it, Kant saw fit to divide the question into three: 1) How are the synthetic a prioriВ propositions of mathematics possible? 2) How are the synthetic a prioriВ propositions of natural science possible? Finally, 3) How are the synthetic a prioriВ propositions of metaphysics possible? In systematic fashion, Kant responds to each of these questions. вЂњHow are synthetic a priori propositions possible? This question is often times understood to frame the investigations at issue in KantвЂ™s Critique of Pure Reason. вЂњI have therefore found it necessary to deny knowledge, in order to make room for faith.вЂќ But this benefit becomes positive as soon as we become aware that the principles with which speculative reaВ son ventures beyond its boundary do not in fact expand our use of reason they unfailingly narrow it, as we find when we examine them more closely.вЂќ вЂњA cursory survey of this work will leave one with the impression that such a metaphysics benefits us only negatively, viz., by instructing us that in speculative reaВ son we must never venture beyond the boundary of experience and this instruction is indeed its primary benefit. Hence it can complete its work and put it aside for the use of posterity, as capital that can never be increased.вЂќ

вЂњOnce metaphysВics has been brought by this critique onto the secure path of a science, it is able to encompass completely the entire realm of the cognitions pertainВ ing to it. вЂњFor the main question is always this: what, and how much, can unВderstanding and reason cognize independently of all experience?вЂќ He is attempting to maintain both the authority of reason with the authority of religion. CPR shows that a critique of reason through the means of reason alone is able to bound the domain of reason to its appropriate use, namely science and math but not metaphysics and religion. This mechanistic view coupled with the universal urge to put ideals under the microscopic of rational criticism threatened traditional moral and religious beliefs. Kant wrote CPR in the age of the enlightenment which was an age of sharp criticism founded on a mechanistic metaphysics influenced by Newtonian physics.

Critique of pure reason