 … Now we have found an answer to the question, “How do we decide whether or not to believe a conditional statement?” the problem is to make the transition from belief conditions to truth conditions; that is, to find a set of truth conditions for statements having conditional form which explains why we use the method we do use to evaluate them. The concept of a possible world is just what we need to make this transition, since a possible world is the analogue of a stock of hypothetical beliefs. The following set of truth conditions, using this notion, is a first approximation to the account that I shall propose: