出典:Wikipedia
出典:『Wikipedia』 (2011/05/06 01:52 UTC 版)
In logic, a strict conditional is a material conditional that is acted upon by the necessity operator from modal logic. For any two propositions p and q, the formula
says that p materially implies q while
says that p strictly implies q. Strict conditionals are the result of Clarence Irving Lewis's attempt to find a conditional for logic that can adequately express indicative conditionals. Such a conditional would, for example, avoid the paradoxes of material implication. The following statement, for example, is not correctly formalized by material implication.