Man derives his knowledge through reason but the theory of reason is a vicious circle, since the knowledge that ‘knowledge is acquired through reason’ comes through the application of reason. In other words, the knowledge that reason is supreme in all matters related to the process by which a man acquires knowledge is a claim made by reason itself. If you have to critique the knowledge that someone claims to have derived through his reason, then to which mental faculty can you appeal? You have to appeal to reason, as there is no higher judge. But can we trust the critique of a mental instrument that has been conducted by that instrument itself?