To repeat some of what I wrote earlier,
According to Woody Allen, we all know that human existence is meaningless and that it ends, utterly and meaninglessly, with death. We all know this, he thinks, but we hide the horrible reality from ourselves with all sorts of evasions and distractions. Worldly people, for example, imagine that they will live forever and lose themselves in the pursuit of pleasure, money, name and fame. Religious people console themselves with fairy tales about God and the soul and post-mortem bliss. Leftists, in the grip of utopian fantasies, having smoked the opium of the intellectuals, sacrifice their lives on the altar of activism. And not only their lives: Communists in the 20th century broke 100 millon 'eggs' in pursuit of an elusive 'omelet.' Ordinary folk live for their children and grandchildren as if procreation has redemptive power.
Pushing the line of thought further, I note that Allen is deeply bothered, indeed obsessed in his neurotic Manhattanite Jewish intellectual sort of way, by the apparent meaninglessness of human existence. Why does the apparent lack of an ultimate meaning bother him? It bothers him because a deep desire for ultimate sense, for point and purpose, is going unsatisfied. He wants redemptive Meaning, but Meaning is absent. (Note that what is phenomenologically absent may or may not be nonexistent.)
But a deep and natural desire for a meaning that is absent may be evidence of a sort for the possibility of the desire's satisfaction. Why do sensitive souls feel the lack of point and purpose? The felt lack and unsatisfied desire is at least a fact and wants an explanation. What explains the felt lack, the phenomenological absence of a redemptive Meaning that could make all this misery and ignorance and evil bearable? What explains the fact that Allen is bothered by the apparent meaninglessness of human existence?
You could say that nothing explains it; it is just a brute fact that some of us crave meaning. Less drastically, and more plausibly, one could say that the craving for meaning has an explanation in terms of efficient causes, but not one that requires the reality of its intentional object. Let me explain.
Craving is an intentional state: it is an object-directed state of mind. One cannot just crave, desire, want, long for, etc. One craves, desires, wants, longs for something. This something is the intentional object. Every intentional state takes an object; but it doesn't follow that every such state takes an object that exists. If a woman wants a man, it does not follow that there exists a man such that she wants him. She wants Mr. Right, but no one among us satisfies the requisite criteria. So while she wants a man, there is no man she wants. Therefore, the deep desire for Meaning does not guarantee the existence of Meaning. We cannot validily argue, via the intentionality of desiderative consciousness, to the extramental reality of the the object desired.
Nevertheless, if is it a natural (as opposed to an artificially induced) desire we are talking about, then perhaps there is a way to infer the existence of the object desired from the fact of the desiring, that is, from the existence of the desiderative state, not from the content or realitas objectiva of the desiderative state. The inferential move from realitas objectiva to realitas formalis is invalid; but the move from the existence of the state to the reality of its object may be valid.
Suppose I want (to drink) water. The natural desire for water is rooted in a natural need. I don't just desire it, the way I might desire (to smoke) a cigar; I need it. Now it doesn't follow from the existence of my need that there is water hereabouts or water in sufficient quantity to keep me alive, but the need for water is very good evidence for the existence of water somewhere. (Suppose all the water in the universe ceases to exist, but I exist for a little longer. My need for water would still be good evidence for the existence of water at some time.) If there never had been any water, then no critter could desire or need it; indeed no critter could exist at all.
The need for water 'proves' the existence of water. Perhaps the desire/need for Meaning 'proves' the existence of Meaning. The felt lack of meaning -- its phenomenological absence -- is grounded in the natural (not artificial) need for Meaning, and this need would not exist if it were not for the extramental reality of a source of Meaning with which we were once in contact, or the traces of which are buried deep within us. And this all men call God.
Mr. Allen, meet Fr. Garrigou-Lagrange:
Since natural desire can never be in vain, and since all men naturally desire beatitude, there must exist an objective being that is infinitely perfect, a being that man can possess, love, and enjoy. (Beatitude, tr. Cummins, Ex Fontibus 2012, p. 79)
This argument, studied in the context of Aristotelian-Thomistic metaphysics, is more impressive than it may seem. If nothing else it ought to undermine the belief of Allen and his like that it is known by all of us today that human existence is ultimately meaningless.
Here is a video with relevant excerpts from G-L's Life Everlasting and the Immensity of the Soul.