| To suppose X means to pretend to change one's belief for the sake of the argument to include X. How to do so is a decision problem: of the many ways to modify one's beliefs to include X, one should choose the one that best fits with one's epistemic goals. I examine the role of suppositional reasoning in the evaluation of purported scientific explanations of various sorts, based on Hempel and Oppenheim's deductive-nomological and inductive-statistical explanations. First, I present for each type of explanation the suppositional reasoning conditions it must satisfy. For example, the dipping of blue litmus paper in acid (in conjunction with the laws of Chemistry) explains why it turned red only if, when one supposes that the litmus paper was not dipped in acid, one must also give up the belief that it turned red. Second, I argue that a specific decision making method (Isaac Levi's) should be used to determine how one is to change one's beliefs for the sake of the argument in each case. Third, I evaluate in detail whether purported explanations, both intuitively explanatory (such as the litmus paper case) and intuitively non-explanatory (such as the Bromberger's "flagpole" case) satisfy these conditions. Fourth, I show that the suppositional reasoning conditions for explanations, when evaluated correctly, systematically solve the many counterexamples to the original Hempel-Oppenheim model. |
