Abstracts
Richard Bradley (LSE)
"Multidimensional Semantics for Conditionals"
In this paper I argue that Stalnaker’s (1968) project of using the Ramsey Test as a constraint on the truth conditions of conditionals can be realised within a multi-dimensional possible worlds semantics. The essential idea behind this semantics is that sentences are made true by ordered sets of possible worlds, each co-ordinate of which specifies what is or would be true under one or another supposition. The truth or falsity of non-conditional sentences depend only on the first co-ordinate of the possible worlds vector, namely that specifying the actual world under a tautological supposition. The truth of conditional of the form "if A then B", on the other hand, depends on the co-ordinate identifying the counter-actual world under the supposition that A.Given a multidimensional model of this kind, we can ask how agent’s uncertainties defined with the respect to the different dimensions articulate and determine the probabilities of sentences. Conditions on the relationship between these uncertainties sufficient for the truth of Adams’ Thesis for indicative conditionals and for Skyrms’ (1981) corresponding hypothesis regarding the probabilities of counterfactuals are given and shown to explain some important difference in the attitudes we take to the two kinds of conditionals.