The title states my thesis. The ancients knew that without a Saviour (a Messiah) then mortal Man on earth was doomed to a more-or-less unhappy situation. I believe that this was understood implicitly, because the ancient religions (including the religion of the ancient Hebrews of the Old Testament) was uniformly pessimistic - grim and harsh.
The most one could claim for ancient religion was that it was not uniformly hope-less (although some kinds of paganism seem to be utterly without hope). For instance, we know that the ancient Hebrews had hope of being saved in some ultimate sense - saved from the otherwise necessarily miserable fate of Man.
But my point is simply that the ancients understood that the basic human situation, mortal life in this world, was literally hope-less. They did not necessarily argue this, they simply perceived it, understood it, knew it.
The situation still broadly prevails among what might be termed 'serious religions' around the modern world - the basic human situation for these is, in its essence, pessimistic, grim, harsh. Their 'hope' is merely for an end to suffering, at most a permanent state of un-aware bliss. In other words the 'hope' is a death that is true extinction of thought, awareness.
The 'hope' of the self is destruction of the self. The 'hope' is that we cease to be.
How come that we moderns no longer know this? How come we moderns cannot understand the basic human situation and the necessity of a saviour if life is to be hopeful and optimistic? How come we generally regard the claims of Christ to be the Messiah as simply superfluous or incomprehensible?
How come we suppose that we can simply choose believe there is no God, or believe in a God but not a Saviour - and that this makes no difference to life!
My point here is not that Jesus is the Saviour - but more basic than that. My point is that we apparently cannot perceive that a Saviour is required if life is not to be hope-less; and that it was only the hope of a Saviour which stopped the ancients from despairing (because despair is the inevitable consequence of having no hope).
Properly understood, the situation seems to be unavoidable and inevitable: No belief in a Saviour means pessimism; and no hope of a Saviour means pessimism plus despair.
Small wonder, then, that our civilization despairs! The extraordinary thing is that we do not even understand why we despair. Indeed we actively-deny the real reason for our intractable despair.
We may or may not personally believe that Jesus Christ really was The Saviour (that is not susceptible of conclusive proof either way, but requires a voluntary choice: requires faith) - but we have reached the extraordinary situation that we do not even understand the that there is anything that we need to be saved-from!