The author proposes that the humanities are no longer the fertile source of important ideas they once were, and attributes this, somewhat vaguely (the vagueness

The author proposes that the humanities are no longer the fertile source of important ideas they once were, and attributes this, somewhat vaguely (the vagueness appropriately matches available information sources on the subject, though), to the humanities fumbling somewhat in the past 40 years or so with certain trends they pushed; to the progress of their analysis perhaps inevitably leading to a direct study of the human mind, which is more expertly carried out by cognitive scientists; and to the general, unaccounted for, contemporary success of science. It seems more likely to me that differences in society's communication structure and regular inability to determine who intellectual leaders are except retrospectively, are the main causes for the changes described by the author. Aside from that, there's probably more of a shift in what the author now considers an important idea than anything: the humanities and sciences address different subject matters. Scientific discoveries often serve to restrict the realm of viable philosophies (e.g. cognitive science's impact on the any theory of innate knowledge a la Plato), but if it ever says something positive on a philosophical subject, that subject is no longer philosophy proper—and there's plenty of room for philosophy still. The rest of the humanities, from my understanding, is about communicating ideas about human life—often times about the experience of living it—using a different set of techniques than the sciences, and the utility of those techniques has not diminished.