Abstract

The three laws of thought are regarded as the axioms. Nevertheless, if they are true in any case, can such a sentence as ‘the present King of France is bald’, according to the law of excluded middle, be true or false in the current circumstances in which he does not exist and it is implausible to ascertain whether he is bald? That is precisely the philosophical puzzle pertaining to the applicability of the laws of thought. Bertrand Russell (1905), when encountering this predicament, established his theory of descriptions, on which the aforementioned sentence could be interpreted as a conjunction of three propositions, and could be considered false. P. F. Strawson (1950), however, refuted Russell’s theory. In Strawson’s view, the use of the sentence which presupposes the existence of a nonentity, is neither true nor false. The puzzle accordingly remains. The puzzle is, this article conceives, engendered by the disregard or nonacceptance of multiple-valued logic. The object of this article is to propose a scheme which extends the use of a proposition to the valuation rules in logic, saves the applicability of the laws of thought to a verifiable or falsifiable proposition. Consequently, the laws of thought are inapplicable solely to an unverifiable and unfalsifiable proposition in the scheme.

Keywords: laws of thought, multiple-valued logic, nonentity, theory of descriptions