The article is a critique of the increasingly navel-gazing direction literary criticism has taken.
It would be a mistake to paint all the "humanities" with the same brush, particularly philosophy (which is more like the wayward, less rigorous brother of math than any of the other humanities) and history (which actually deals with factual content). In fact, "the humanities" is probably a mistaken grouping for these subjects, since they vary widely.
Mathematics isn't that rigorous, I think you've been misinformed.
history (which actually deals with factual content)
Uh, not so much. Lots of documents and facts are missing and we have only guesses to work with. Mind you, they're good or even great guesses, but there are still some doubts.
Yet they differ fundamentally as history is based on fact, philosophy on logics, psychology and sociology on sort of both, while literature can be anything from entertainment, mostly entertainment, to philosophy.
It would be a mistake to paint all the "humanities" with the same brush, particularly philosophy (which is more like the wayward, less rigorous brother of math than any of the other humanities) and history (which actually deals with factual content). In fact, "the humanities" is probably a mistaken grouping for these subjects, since they vary widely.