And I think you've clinched it in calling it a philosophy which I think is the point where they stopped and possibly drew back.
Can you give a deep and well thought through philosophy?
Probably not a philosophy which would satisfy you. I can only point out what I realised were the drawbacks and inconsistencies of French existentialism (which is basically that of Sartre, the Prof has noted - others were largely parasitic on his views. Sartre himself claimed indebtedness to Heidegger, whereas H himself called L'Etre et Le Neant unreadable dreck). Well, I'm not going to give a full resume of French existentialism either, but here are a few points. Though it doesn't actually deny unconscious processes in the human organism, it wishes to nullify their importance to insignificance. As many contributors to this forum have often pointed out, unconscious processes are practically everything that govern us, even down to the decisions we think we make with the pre-frontal cortex.
Sartre in particular seemed obsessed in asserting a 'self' against what he perceived as the nothingness of being (this, along with mescalin, no doubt, prompted his agonisings about 'the Abyss). His way of asserting selfhood and freedom was to prove his existence by a succession of
actes gratuits which run counter to all nature's constraints (the idea began with the novelist Gide). That's a pretty hopeless scenario - no one can hope to behave in this unpredictable way at every moment, and of course, no one has ever done.
For better or worse, we are bound up with the whole of nature and the universe, and such frantic self-assertion is the act of people who have lost any sense of unity with the world. By saying that, I'm not letting 'spirituality' in by the back door. We may be made of 'star-stuff', but that doesn't mean the universe is sentient.
Sartre was a good novelist, I think, and dramatist. Such a pity he couldn't see through Stalin. But that resulted from another of his benighted mental escapades - the attempt to link existentialism and Marxism. At the risk of being accused of dragging in an
argumentum ad consequentiam , I'll shut up.
That'll do yer.