Let us note here that the same formal analysis ... applies to scientific prediction as well as to explanation. The difference between the two is of a pragmatic character. If E is given, i.e., if we know that the phenomenon described by E has occurred, and a suitable set of statements C1, C2, ... Ck, L1, L2, ... Lr is provided afterwards, we speak of an explanation of the phenomenon in question. If the latter statements are given and E is derived prior to the occurrence of the phenomenon it describes, we speak of a prediction.
Carl G. Hempel (b. 1905), U.S. philosopher of science, logical positivist, and Paul Oppenheim. repr. In C.G. Hempel, Aspects of Scientific Explanation, pp. 245-295 (1965). Originally appeared in Philosophy of Science XV, "Studies in the Logic of Explanation," (1948).
The famous statement of the "symmetry thesis" regarding scientific explanations and scientific predictions.