Historical Necessity and Conditionals
Donald E. Nute · Noûs · 1991
Despite the attention conditional logic has received since Stalnaker's seminal paper [1968], few papers have appeared that explore the role tense plays in the truth conditions of conditionals. I will develop a semantics for a formal language containing tense operators, a historical necessity operator, and a conditional operator. In developing this semantics, I will assume an indeterministic stance and suppose that future tense statements generally lack truth values. The semantics will include possible worlds and pseudo-branching time. I will argue that the technical notion of an actual world makes no sense from this Aristotelian perspective and should be replaced with the notion of an actual manifold, a set of worlds that has not yet been ruled out by either history or physics. I will defend two main conclusions in the paper, one negative and one positive. The negative conclusion is that we cannot in general represent English conditional sentences by combinations of conditional operators and standard tense operators. The positive conclusion is that all true intensional conditionals are historically necessary and all false intensional conditionals are historically impossible.