Suppositional Reasoning in Scientific Explanations

To suppose X means to pretend to change one's belief for the sake of the argument to include X. 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 for each type of explanation I present the suppositional reasoning conditions it must satisfy. 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 and intuitively non-explanatory satisfy (or do not satisfy) these conditions. Fourth I show that the suppositional reasoning conditions for explanations when evaluated correctly systematically solve the many problems of the original Hempel-Oppenheim model of explanations.