 … While explanation, prediction, and postdiction are alike in their logical structure, they differ in certain other respects. For example, an argument [like Figure 4 above] will qualify as a prediction only if [its explanandum] refers to an occurrence at a time later than that at which the argument is offered; in the case of postdiction, the event must occur before the presentation of the argument. These differences, however, require no further study here, for the purpose of the preceding discussion was simply to point out the role of general laws in scientific explanation, prediction, and postdiction (Hempel 1958: 37–38).