These two readings are closely related. Okasha begins (pp. 40-45) with an outline of a theory of explanation that is most closely associated with Carl Hempel, and the paper on JSTOR is one of the first presentations of that idea. Okasha’s account of Hempel’s views is even close in order to the the presentation Hempel offers. (Hempel counts Paul Oppenheim as a joint author, but it seems that Hempel was responsible for the writing.)

On pp. 40f, Okasha notes that it is possible to object to Hempel’s account of explanation in two ways, holding that it is too strict or that it is too liberal. Okasha considers only objections of the latter sort, but many objections of the former sort are along the lines that Hempel considers in regard to the claim that explanations are potentially predictions (see pp. 138f in Hempel and Oppenheim).

Okasha considers objections to the account as too liberal under the two headings of symmetry (pp. 45-47) and irrelevance (pp. 47-48). These objections serve to motivate the alternative accounts of explanation that you will find in the reading assignments for Thursday, so our discussion of them will continue then.

One point in Okasha’s presentation of the first objection could be confusing: when he says that “the covering law model implies that explanation should be a symmetric relation” (p. 47), you should take him to be speaking only of the kind of case he has been considering. It is not always possible to reverse the roles of the explanandum and one of the particular facts in the explanans while maintaining the deductive character of the explanation. Nonetheless, the temporal reversibility of most physical laws means that this will often be possible.

I have recommended §4 in Hempel and Oppenheim because it adds many examples and indicates the scope they saw their account as having. But I have only recommended it because many of the objections they anticipate and respond seem less pressing now than they may have 60 years ago. For example, the “neo-vitalist” position they mention on pp. 145f was associated with Hans Driesch (1867-1941), who did important experimental work in embryology early in the 20th century and went on in the following decades to develop a position on the philosophy of biology based on an idea of “entelechy” that he held to be fundamentally different from the concepts of the physical sciences.