One point that deserves emphasis here is the non-equation of pessimism with theories of decline.  While pessimists may posit a decline, it is the denial of progress, not an insistence of some eventual doom, that marks out modern pessimism.  Pessimism, to put it precisely, is the negation, not the opposite, of theories of progress.  This may immediately strike some readers as a fudge, but consider: most of those thinkers whom we could agree without argument to call pessimists, like Schopenhauer, did not profess a belief in any permanent downward historical trend.  Schopenhauer posits no long-term historical trends at all, merely a constantly regrettable human condition burdened…by linear time.  In fact, belief in a permanent decline of the human condition is relatively rare in political theory….But it is not an accident that writers such as Schopenhauer are known as pessimists–for the nonprogressive yet linear view of human existence is indeed profoundly discomfiting.  Unlike a cyclical account, where the pattern of history is essentially pregiven, pessimism is historical in the modern sense: change occurs, human nature and society may be profoundly altered over time, just not permanently for the better. ~Joshua Foa Dienstag, Pessimism: Philosophy, Spirit, Ethic

Obviously, I am sure that even pessimists cannot show change in human nature over time one way or the other, just as meliorists and optimists cannot.  It is this constancy of human nature that convinces me that the pessimists are on the whole right, or at least more likely to be right, because even with institutional, social or political change man remains unchangeably man (even the Christian belief in grace and deification does not really overthrow this constancy of nature, so much as it transforms the quality and purpose of the energies of man–grace and deification do not really change human nature so much as they restore and fulfill it to its true purpose).

As for the lack of long-term trends in history, I am completely in agreement with the pessimism outlined here.  It is my firm conviction that believers in progress are able to believe in it largely through ignorance of human history or because of a particularly biased Hegelian idea of History, so that you can still have inexplicably prominent people use the phrase, “History is against this or that,” as if History were out there somewhere expressing a firm opinion about a topic.

In spite of what I have already said on this, someone may still object that it is impossible to embrace the Gospel and pessimism, when one of the tenets of pessimism (as Dienstag lays out elsewhere) is that human existence is absurd.  But without the Gospel, without the extraordinary act of God entering history and redeeming man, human existence would be absurd after a fashion.  The pessimists do not tell the entire story, but they do largely correctly assess the state of the world and they certainly tell more of the real story than the optimists who would generally like to rewrite the story.