The romantic philosophers, Nietzsche, Kierkegaard, who so moved the twentieth century in its private moments, in its moments of 'culture', these philosophers are characterised by their reaction to the end of established Christianity. Heidegger, he has no like, and stands aloof from everything else around him, putting into thought what it meant to have been a Christian. Conceptualising, that is the extremely foundational and totally obscure fact that being 'alive' is inexplicable. Just 'being here' has, he said, hardly been discussed at all in philosophy. The owl of wisdom takes flight as darkness falls, and just so, it was only when religion and philosophy and general Western culture had collapsed that he was able to spell out (very confusedly) the bedrock on which Christianity and all human life is built.
What is the basis for everything else? What is the deepest fact about which we can have knowledge? It is that there is existence and consciousness of it. That we are alive, and that we might be or soon will be no longer existing or conscious. Unless there is some eternal world and eternal self, then once again there will be complete nothingness and darkness once we, inevitably, disappear.
For me, surveying them and reading their own historical surveys of philosophy and philosophers, it has become apparent that knowledge (philosophy) has never grasped what it is that, our very existence is an empty nothingness without a method of meditation and a link to God. That is, the true approach to the truth must presuppose that a man is not a real man until he has recognised as a philosophical fact, that both sin and prayer are essential determinants of what the mind is. If you don't first pray to God and recognise as a fact your eternal life, then you are working with a defective instrument. The instrument of rationality, should be working at the service of a heart which is turned to God in order for it to practice real philosophy.
This needs, I think, spelling out.