  Quine does not accept the general counterfactual idiom, “if X were to happen then Y would happen”, as part of regimented theory. As in the case of belief, the unrestricted use of this idiom allows us to form sentences whose truth-conditions are, at best, unclear. A famous example is the pair, presumably alluding to the Korean war of the early 1950s: “If Caesar were in charge he would use the atom bomb”; “If Caesar were in charge he would use catapults” (see Quine, 1960, 222); they seem equally plausible but they cannot both be true (for a response, see Lewis 1973). In such cases, we have no reason to think that some (physical) fact is being claimed. Many dispositions, however, are perfectly acceptable by Quinean standards. To call the glass fragile is to attribute to it a structure which would lead its breaking under certain circumstances; the structure is a physical state, even if we cannot in practice specify it in physical terms.