conditionals

   Conditionals are 'if-then' statements or the propositions expressed by 'if-then' statements. They fall into two main classes: material conditionals, such as 'If Oswald did not kill Kennedy on 22 November 1963 then somebody else did', and subjunctive conditionals, such as 'If Oswald had not killed Kennedy on 22 November 1963 then somebody else would have done.' That these two conditionals are different in meaning is apparent from the fact that most think the first is true but the second false. The 'if' part of the conditional (or the proposition it expresses) is called 'the antecedent' and the 'then' part (or the proposition it expresses) is called 'the consequent'. Counterfactuals are subjunctive conditionals whose antecedents are false (or express false propositions). The standard semantics for counterfactuals, developed by David Lewis and Robert Stalnaker, is, roughly, that a counterfactual is true if its consequent is true in the closest possible world in which the antecedent is true, and that counterfactuals with necessarily false antecedents are vacuously true. Christian philosophers have been interested in this last contention: since God necessarily exists, the statement 'If God had not existed everything else would have been much as normal' is vacuously true on the standard semantics, yet one thinks intuitively that it is false. One project of analytical Christian philosophy is to work on a better semantics for such conditionals, though there is no agreement on such a system of semantics as yet.

   See logic

   Further reading: Beaty 1990; Jackson 1987; Jackson 1991; Lewis, David K. 1986a; Stalnaker 1999