A form of implication involving only a weak connection between the propositions
related. A proposition P materially implies another proposition Q if and only if either P is false or Q is
true (or both). It occurs in a stronger form as logical implication, which is the form of implication used in mathematics and some formal semantics, but logical implication is too strong to be useful in most ordinary contexts. The philosopher David K. Lewis and others have attempted to develop a logic of relevant implication, but material implication is still more commonly used
in philosophy.