Thinking and Being

Opposing a long-standing orthodoxy of the Western philosophical tradition running from ancient Greek thought until the late nineteenth century, Frege argued that psychological laws of thought--those that explicate how we in fact think--must be distinguished from logical laws of thought--those that formulate and impose rational requirements on thinking. Logic does not describe how we actually think, but only how we should. Yet by thus sundering the logical from the psychological, Frege was unable to explain certain fundamental logical truths, most notably the psychological version of the law of non-contradiction--that one cannot think a thought and its negation simultaneously.