"Criteriology is the science of true and certain knowledge," (1) and is mainly interested in the problem as to whether man can know things and have a true and valid knowledge of theme as they are in reality. It is concerned with the fact of truth and error in the philosophic and scientific fields, it points out that basis in reality upon which man can build all his knowledge an in virtue of which he can distinguish truth from error. Every problem of philosophy is really a problem of knowledge. We must distinguish truth from error. The study of the criterion of truth will enable us to make this distinction. In practical usage the word criterion is the norm, or yardstick by which we distinguish truth from falsity. In the theoretical field criteriology has a basic value in that if we could not know truth with certitude philosophy and science would be impossible, study would be useless, and man's desire for truth would be futile.