Is logic, as Arnauld would have it, merely a tool of clear thinking in order to aid rhetoric, or does it reflect universal laws of thought that correspond to reality? This latter view, to which Arnauld and the Port Royal logicians were hostile, holds that there are three laws of thought that are necessary principles for any rational creature, even God. These are the law of non-contradiction, the law of identity, and the law of the excluded middle. These state respectively that a proposition cannot be simultaneously asserted and denied; that if A is identical to B, then anything that is true of
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