Counterfactuals and Possible Worlds

This article is a selective review of David Lewis's Counterfactuals (Cambridge, Mass., 1973), a challenging, provocative, absorbingly interesting attempt to analyze statements of the form “If it were the case that P, then it would be the case that Q.” I shall follow Lewis in calling these “counterfactuals,” and shall nearly follow him in abbreviating them to the form P→Q. Chapter 1, which is nearly a third of the whole, gives the analysis and proves that it endows counterfactuals with some properties which they evidently do have. Chapter 2 presents some “alternative formulations” of the analysis—a logical jeu d'esprit which I shall not discuss except for the section ( § 2.6) about “cotenability.”