The idealist is bound in the end to substitute himself for the Mind and then we have an individual to deal with. Let us confront him with the (as he thinks) shocking spectacle of a Christian astronomer. How can an astronomer believe in the Incarnation or go to Mass? The idealist's only hope is to put up a distinction. As an astronomer, this monster (or rather this amphibian) is a man of the twentieth century and the idealist can greet him as a contemporary. As a man who believes in the Incarnation, however, and goes to Mass, he is behaving like a mediaeval or a child; and this is a pity. When we ask the philosopher to justify his extraordinary dichotomy, he may call upon Reason and Mind till he is black in the face, but he will not convince us; especially when we see that he does not scruple to use psychological and even sociological arguments to account for these survivals in the astronomer, while he absolutely forbids us turn such arguments or analyses upon himself. He is a man of 1930 from top to toe. And yet he is still invoking an eternal Mind, but a Mind which has none the less been born; who Its next incarnation will be, Heaven only knows. Frankly, I find all this extremely incoherent. If a Marxist, for example, were to tackle the idealist and tell him plainly that his Mind was a purely bourgeois product begotten of economic leisure, the idealist would have to take refuge in the realm of completely bloodless abstractions. I think myself that idealism of this kind cannot help being cornered, with concrete religious philosophy hemming it in on one side, and historical materialism on the other. For it is in fact impotent when confronted with history any real history, even if it is just the history of a single life. It has no feeling for tragedy, and (what is worse) no feeling for flesh and blood either. Personally, I think that people who substitute the Cartesian concept of matter for the richly confused idea of the flesh which is embedded in all Christian philosophy are doing anything but progressing in their metaphysics. There is an almost untouched task here, and pure metaphysicians would do well to focus all their attention upon it, or so I think: the task of describing the evolution and progressive confusion of the notions of flesh and fleshly existence in the history of philosophical thought.
At bottom, this idealism is a purely professorial doctrine, and falls directly under Schopenhauer's partially unjust criticism of the academic philosophers of his day. (It was partially unjust, because there is a real feeling for concreteness and human drama in such writers as Schelling and Hegel.)
In point of fact, philosophical idealism would very likely have had no appreciable effect upon the development of human thought, had it not found a redoubtable ally in all forms of applied science. I believe that the spirit of applied science is really in itself the most serious obstacle, for many perfectly candid minds, to the acceptance of the notion of religious life, or rather religious truth.
(from: Gabriel Marcel: Some Remarks on the Irreligion of Today, 1930)