Four Decades of Scientific Explanation

The search for scientific knowledge extends far back into antiquity. At some point in that quest, at least by the time of Aristotle, philosophers recognized that a fundamental distinction should be drawn between two kinds of scientific knowledge—roughly, knowledge that and knowledge why. It is one thing to know that each planet periodically reverses the direction of its motion with respect to the background of fixed stars; it is quite a different matter to know why. Knowledge of the former type is descriptive; knowledge of the latter type is explanatory. It is explanatory knowledge that provides scientific understanding of our world. Nevertheless, when Aristotle and many of his successors down through the centuries tried to say with some precision what constitutes scientific explanation they did not meet with great success. According to Aristotle, scientific explanations are deductive arguments; as we shall see, this idea has been extraordinarily influential. But as Aristotle clearly recognized, not all deductive arguments can qualify as explanations. Even if one accepts the idea that explanations are deductive arguments, it is no easy matter to draw a viable distinction between those arguments that do qualify and those that do not. Forty years ago a remarkable event occurred. Carl G. Hempel and Paul Oppenheim published an essay, "Studies in the Logic of Explanation," which was truly epoch-making. It set out, with unprecedented precision and clarity, a characterization of one kind of deductive argument that, according to their account, does constitute a legitimate type of scientific explanation. It came later to be known as the deductive-nomological model. This 1948 article provided the foundation for the old consensus on the nature of scientific explanation that reached its height in the 1960s. A large preponderance of the philosophical work on scientific explanation in the succeeding four decades has occurred as a direct