The authors outline a theory of conditionals of the form If A then C and If A then possibly C. The 2 sorts of conditional have separate core meanings that refer to sets of possibilities. Modulation can add information about temporal and other relations between antecedent and consequent. 9pZV)1, 2 where the former holds factually, and the latter A Uniform Theory of Conditionals 3 the philosophy of science on inference and inquiry.4 Why seek such alignment? A uniform theory of conditionals is one which compositionally captures the behavior of both indicative and subjunctive conditionals without positing ambiguities. A THEORY OF SUBJUNCTIVE CONDITIONALS 1. This chapter was the first exposition and defense of an axiom system and model theory for a conditional logic in the possible worlds framework, a theory designed to model counterfactual propositions. Knowledge, pragmatics, and semantics can modulate these meanings. The authors outline a theory of conditionals of the form If A then C and If A then possibly C. The 2 sorts of conditional have separate core meanings that refer … This paper raises new problems for the closest thing to a uniform analysis in the literature (Stalnaker, Philosophia, 5, 269–286 (1975)) and develops a new theory which solves them. One is that the constructive empiricist make do with what his theory says is observable; but this will not provide a full demarcation. It is argued, using a version of the Ramsey test, that the truth-conditions for conditionals that are provided can explain why we assess counterfactuals in the way we do. Leibniz, Boole, Frege and others established the idea of language as an epis-temic tool, and conditionals inhabit a A SIMPLE THEORY OF CONDITIONALS 233 replies to this objection. Introduction Trivially true conditionals can evolve inferentially, under Modus Ponens, from any premisses rFeal and r(1.q .Z. Another is that the constructive conditionals advanced inGillies(2009) andStarr(to appear) and transforms it into a uniform theory of conditionals that explains the basic contrasts be- tween the two varieties by paralleling the extension/revision contrast.