Attempts have been made to define “truth” in terms of “knowledge,” or of concepts, such as “verifiability,” which involve “knowledge.” Such attempts, if carried out logically, lead to paradoxes which there is no reason to accept. I conclude that “truth” is the fundamental concept, and that “knowledge” must be defined in terms of “truth,” not vice versa. This entails the consequence that a proposition may be true although we can see no way of obtaining evidence either for or against it. It involves also a partial abandonment of the complete metaphysical agnosticism that is favoured by the logical positivists.
Bertrand Russell (from An Inquiry into Meaning and Truth, 1950)