Single Idea 5396

[catalogued under 2. Reason / B. Laws of Thought / 1. Laws of Thought]

Full Idea

For no very good reason, three principles have been singled out by tradition under the name of 'Laws of Thought': the laws of identity ('what is, is'), contradiction ('never be and not be'), and excluded middle ('always be or not be').

Gist of Idea

Three Laws of Thought: identity, contradiction, and excluded middle

Source

Bertrand Russell (Problems of Philosophy [1912], Ch. 7)

Book Reference

Russell,Bertrand: 'The Problems of Philosophy' [OUP 1995], p.40


A Reaction

'For no very good reason' seems a bit unfair, probably to medieval logicians, who deserve more respect. Russell suggests that the concept of implication deserves to be on the list. Presumably optimism about thinking is a presupposition of thought.