law of excluded middle

American  

noun

Logic.

1. the principle that any proposition must be either true or false.

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Example Sentences

The law of Excluded Middle contains an extension or doubling of the law of Identity, in that the identity here appears, not in the form of consistency, but in that of contradiction; as, "either—or."

From Project Gutenberg

The certainty afforded in the law of Identity in positive form, in the law of Contradiction in negative form, in the law of Excluded Middle in the form of an opposition, and in the law of Sufficient Reason in conditional form, is based upon Causality, Community of Species, or Totality.

From Project Gutenberg

But though the law of Excluded Middle must hold good here as elsewhere, it is also to be noticed that the absence of proof in the natural order of things, with respect to the non-existence of transcendental causes, is not equivalent to the presence of proof of the opposite.

From Project Gutenberg

I concluded that the maid was uncertain as to the objective validity of the law of excluded middle, and remarked that to her mistress.

From Project Gutenberg

Take, for example, the law of excluded middle in the form ‘all propositions are true or false.’

From Project Gutenberg