Page "Reason" Paragraph 90

Since the 17th century rationalists, reason has often been taken to be a subjective faculty, or rather the unaided ability ( pure reason ) to form concepts.

For Descartes, Spinoza and Leibniz, this was associated with mathematics.

Kant attempted to show that pure reason could form concepts ( time and space ) that are the conditions of experience.

Kant made his argument in opposition to Hume, who denied that reason had any role to play in experience.