The essence of that post-metaphysical philosophy is summed up in that phrase of Sartre: "We can go no further." What he meant to say was that philosophy cannot go as far as the universe. This was exactly Kant's major contention. But this is exactly what many scientific cosmologists, and scientists in general, find difficult to accept since Einstein published that great memoir of his in 1917. This is not to say that prior to that scientists in general doubted the existence of the universe. They always felt it in their bones that scientific findings, insofar as they helped establish scientific laws, had universal significance or a signification relating to the universe itself. They knew this long before Popper testified to an old truth with a new phrase, namely, that all science is cosmology. But since that memoir of Einstein no one can repeat Kant's cosmological antinomies and still appear scientific, a trick by which Kant had set so great a store.
Those philosophers who try to dissipate the great shadow which Einstein is casting on them can do no better than be very brief about Einstein's science. And lest they should thereby appear either incompetent or contemptuous, they should follow Sartre's art of throwing a red herring in the form of a pleasing but brief metaphor. "Life is limited by life: it becomes like the world of Einstein, finite but unlimited," - was Sartre's sole reference to Einstein's cosmology in a context that dealt with being as very distinct from nothingness.
Indeed, for Einstein the world was a being, and the most encompassing being at that. For him the universe was not his world, the world of his ideas, but a reality best revealed by the best in science. He was most conscious on this point. A decade before Sartre was to reject the Nobel Prize in literature in 1965, there appeared in Paris the correspondence between Einstein and M. Solovine, his friend from student days. To Solovine's query whether Einstein had become a believer, nay a Catholic, on the basis of his cosmology, Einstein replied, of course, in the negative. But he also stated that only the step from the universe to God was illegitimate but not the march to the universe itself.
Einstein, of course, thought that science took him as far as the universe. It did not. Science does not take the scientist even as far as the reality of his most trivial scientific instruments. The scientist assumes the reality of things before he can engage in his only legitimate business which is to establish the quantitative properties of things existing. Reasoned discourse about the existence of things is the very business of that ontology for which modern philosophy has no use. Ontology is subtly reduced to the art of aping what science does when one reads with approval W. Quine's declaration: "To be, I have persistently held, is to be the value of a variable." Obviously, Quine did not mean Aristotle's or Thomas's analogy of being. Although they both admitted the various realizations of being, they did so only because they held, in their own ways, that there was an ultimate being which was not variable.
[SLJ Universe and Creed 64-6, emphasis added]
"Reason is itself a matter of faith."
[GKC Orthodoxy CW1:236]
Without pretending to span within such limits the essential Thomist idea, I may be allowed to throw out a sort of rough version of the fundamental question, which I think I have known myself, consciously or unconsciously since my childhood. When a child looks out of the nursery window and sees anything, say the green lawn of the garden, what does he actually know; or does he know anything? There are all sorts of nursery games of negative philosophy played round this question. A brilliant Victorian scientist delighted in declaring that the child does not see any grass at all; but only a sort of green mist reflected in a tiny mirror of the human eye. This piece of rationalism has always struck me as almost insanely irrational. If he is not sure of the existence of the grass, which he sees through the glass of a window, how on earth can he be sure of the existence of the retina, which he sees through the glass of a microscope? If sight deceives, why can it not go on deceiving? Men of another school answer that grass is a mere green impression on the mind; and that he can be sure of nothing except the mind. They declare that he can only be conscious of his own consciousness; which happens to be the one thing that we know the child is not conscious of at all. In that sense, it would be far truer to say that there is grass and no child, than to say that there is a conscious child but no grass. St. Thomas Aquinas, suddenly intervening in this nursery quarrel, says emphatically that the child is aware of Ens. Long before he knows that grass is grass, or self is self, he knows that something is something. Perhaps it would be best to say very emphatically (with a blow on the table), 'There is an Is". That is as much monkish credulity as St. Thomas asks of us at the start. Very few unbelievers start by asking us to believe so little. And yet, upon this sharp pin-point of reality, he rears by long logical processes that have never really been successfully overthrown, the whole cosmic system of Christendom.
[GKC St. Thomas Aquinas CW2:528-9]