The year 1982 marks the twentieth anniversary of Carl G. Hempel's “Deductive-Nomological vs. Statistical Explanation,” published in Minnesota Studies in the Philosophy of Science, volume III. This work constitutes, to the best of my knowledge, the first extended and systematic philosophical treatment of statistical or probabilistic explanation, and the first serious attempt to articulate explicitly a precise model for such explanations. Because of this fact, it seems to me, we may take 1962 as the year in which the philosophical theory of scientific explanation first entered the twentieth century. By that time, virtually every branch of empirical science made indispensable use of statistical methods and most of them counted statistical generalizations among their important results.