Still more unequivocal was the sceptical nihilism expressed by Gorgias: - (I) nothing exists; (2) if anything existed, it would be unknowable; (3) if anything existed and were knowable, the knowledge of it could not be communicated.
The prominence given by most of the Sophists to rhetoric, their cultivation of a subjective readiness as the essential equipment for life, their substitution of persuasion for conviction, all mark the sceptical undertone of their teaching.
2 It may be as well to add that the sceptical side of Kantianism is mainly confined to the Critique of Pure Reason, but this side of Kantian thought has been most widely influential.
Even in that book Hume is able to play with sceptical solutions.
The key to Reid's philosophy is to be found in his revulsion from the sceptical conclusions of Hume.