One remarkable feature of the “existence” concept is that essentially no one—in either the Buddhist or Western traditions—even tries to explain what it is supposed to mean. It’s assumed that everyone knows—but no one can say. The harder you look into it, the less coherent and consequential the idea becomes. (I plan to write about this at length someday; there’s a stub version here.)
I don't see why a man should despair because he doesn't see a beard on his Cosmos. If he believes that he is inside of it, not it inside of him, he knows that consciousness, purpose, significance, and ideals are among its possibilities, and if he surmises in vacuo that those are all finite expressions inadequate to the unimaginable, I see no more ground for despair than when a Catholic says that he does not know the thoughts and purposes of God. It is a fallacy, I think, to look to any theory for motives — we get our motives from our spontaneity — and the business of Philosophy is to show that we are not fools for doing what we want to do.