Writers of various sorts, you may have noticed, sometimes take a notion to cast aside their particular genre or discipline and Just Write About Life: you know, about Everything-The Big Picture, The Whole Enchilada, What It All Means, and all that.
Long ago and far away, when a writer got that urge there was only one thing to do: Turn to theology. We're talking about your Augustine, your Aquinas, your Luther. They really said it All, and at length, with lots and lots of capital letters.
When the church business lost some of its shine in later centuries, your philosophers did essentially the same thing. Kant, Hegel, and Marx were all great synthesizers aiming for their own special Summa. When Western Homo sapiens started to lose faith-not only in God, but in reason, too-it was the artist's turn. From at least the mid-19th century onward, the mind that sought to wrap itself around the whole of its time, and get it all down, would find expression in The Novel. Here come Dickens, Melville, Eliot, Faulkner, Cather.
This is the age that is dying just now. There are a few Novelists of this sort still around-Norman Mailer, Toni Morrison, E.L. Doctorow, maybe Joyce Carol Oates. Maybe you can come up with a couple more, but that's about it...which is just as well because hardly anyone reads them anymore.
These days the writer who aims to take in the whole of life and really get the old zeitgeist by the tail should probably become a TV critic. This explains why, with at least a toe in the door of the media crit biz, I've spent a significant chunk of the last few years trying to become a novelist (to little avail, yet). "Right guy, wrong century," the tombstone will say.