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laws of thought
logic
laws of thought, traditionally, the three fundamental laws of logic: (1) the law of contradiction, (2) the law of excluded middle (or third), and (3) the principle of identity. The three laws can be stated symbolically as follows. (1) For all propositions p, it is impossible for both p and not p to be true, or: ∼(p · ∼p), in which ∼ means “not” and · means “and.” (2) Either p or ∼p must be true, there being no third or middle true proposition between them, or: p ∨ ∼p, in which ∨ means “or.” (3) If a propositional function ...(100 of 451 words)