Full Idea
The truly critical part of his First Critique was the Transcendental Dialectic; there Kant exposed the Illusions of Reason.
Gist of Idea
Kant exposed the illusions of reason in the Transcendental Dialectic
Source
report of Immanuel Kant (Critique of Pure Reason [1781]) by Bas C. van Fraassen - The Empirical Stance 1.1
Book Reference
Fraassen,Bas van: 'The Empirical Stance' [Yale 2002], p.2