How have philosophers, and others, come to dwell on such phenomena (if they may be called that) as angst, dread, nothingness, anxiety and other such foreboding--what, exactly? Feelings? Things? States? It seems to me a good question, as by my understanding these woeful conditions of mind are said to exist separate from any particular object. That's what distinguishes them from fear, for example. We fear something or someone in particular. The angst, dread, etc. written of by philosophers, usually existentialists, have no particular object as they refer to life, living in general, or the world in general, all their constituents conspiring, as it were, to make us miserable in some profound sense.
Angst seems to have been created by that most melancholy of all Danes, Soren Kierkegaard. Kierkegaard makes Hamlet seem positively jolly. The author of such works as Fear and Loathing and Sickness unto Death wouldn't be the life of any party, except perhaps a burial party, at which he could, I suppose, cheer others present by making comments regarding the good fortune of the deceased to be quit of this vale of tears.
Kierkegaard was a (very sad) man of the 19th century, and it seems the concept of life and the world as full of woe and the relentless urge to expound on that subject in painful though not useful detail developed during the 19th and 20th centuries, at first at least through the efforts of Europeans. I wonder why, and here provide a modest effort at an explanation, or the beginnings of one.
I think of ancient Western philosophy, and I know of no instance where the followers of Plato or Aristotle, the Stoics or Epicureans, or philosophers of any ancient school of which I know felt or described anything even nominally similar to angst, dread, anxiety or any other items in the cornucopia of woe posited by existentialists or nihilists, let alone anti-natalists who go them one better by not only decrying the world but contending it's so full of suffering that it is immoral to have children. Even the Platonists and Neo-Platonists, who thought there was a realm beyond the imperfect world, to my knowledge didn't dread it as a whole.
Something must have happened to change this perception of the world so completely. Ancient Western philosophy, like so much else, was stopped cold by the onset of Christianity, which later tried to assimilate it, though not all of it. Christianity famously condemned the world and all that's in it, including we humans, as sinful and wicked. Like certain ancient philosophers, they thought there was a higher realm. But they thought that realm was available only to Christians, and very good Christians to boot. The ancient pagan philosophers didn't think that the higher realm was available exclusively to any follower of any particular religion.
Christianity began to lose its grip on thinkers and intellectuals from about the 18th century on. Many, like Voltaire, accepted a kind of Deism. But subsequently, those no longer able to accept Christianity or a Christian god found it impossible, for some reason, to accept the world. "Without God, anything is permissible" are the words used by Dostoyevsky in The Brothers Karamazov. Despite the fact that the ancients accepted the world as good, or at least not dreadful, without the need for believing in a personal deity like the one endorsed by Christianity, the intellectuals of the 19th and 20th century could not do so. And so, for them, anything was possible. There was no longer a guide for conduct, no standards to be applied, nothing good or bad, no purpose to life; we're deposited in the world for no reason, only to suffer.
If this hypothesis has any basis, it's striking the extent to which the absence of God, of standards, of morals derived from a creator, rendered the intellectuals of formerly Christian Europe hopeless and in despair. The reaction to the Death of God was dramatic, even melodramatic. The search for alternatives began, but these thinkers had been so convinced of the need for absolute knowledge and standards of conduct that the probable, the likely, the well established didn't suffice to assuage their concerns.
And so nothing quite worked. Nothing replaced Christianity. Existentialism, nihilism, were unsatisfactory and fostered melancholy at best, angst, dread and anxiety at worst. Some became mystics or quasi-mystics, seeing some form of redemption through nationalism and racist ideologies and belief in leaders amounting to demigods.
The result is many of us see the world as not only separate from us, but deadly to us. We're outsiders without hope or function. We have no place to go. For everything, we're out of tune.
Separate from the world, but not beyond it in any permanent sense. Subject to it but incapable of remedying our lot or making things better for us or others, there being no God to tell us that's what we should do. It seems a remarkably self-pitying, futile way to live. If it is the result of a disenchantment with a particular religious view which became rationally unsupportable, however, there are ways to overcome that disenchantment, as the ancients knew but we have forgotten.