Almost all the original philosophers, from Socrates to the verificationists of the present day, have tried to provide some universally applicable method of eliminating confusion and error from our discourse: this provision of a method of ‘correcting the understanding’ is at least one, and perhaps the principal, of the continuous threads which can be traced in Western philosophy. There was the Socratic method, which requires us to look for real definitions of our fundamental abstract terms: the Cartesian methods of rejecting as possible candidates for knowledge any propositions which do not consist of clear and distinct ideas: the Humean or Empiricist method of dismissing as nonsense any non-tautologous statement which cannot be justified as referring to the order of our sensations: Kant's transcendental method of critical philosophy, whichit would certainly be imprudent to characterize in a phrase, but which was equally intended to be a safe protection against empty metaphysics and meaningless questions: lastly, the verification principle, which provides a general method of determining which of our statements conform to some scientific standard of intelligibility, and which are to classed as tautologies or as playing with words. New movements in philosophy have in general been new methods of correcting the understanding, methods which are further generalized and applied in the interval before another great philosopher appears with another general method of showing that all previous metaphysics is nonsense.