C.S. Lewis held to many of the scientific conclusions of his day. Nonetheless, he was often critical of what others have sometimes called “scientism”—a worldview that treats science as a stand-alone teller of truth without a deeper epistemological basis and thus room for a metaphysics; a form of science that makes absolutist exclusive claims that lead it to assume more jurisdiction than its methodological parameters actually allow.

See the following quote from his lecture, “Is Theology Poetry?” or as we might rephrase it, Is Christianity nothing more than aesthetically pleasing mythology?

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“The picture so often painted of Christians huddling together on an ever narrower strip of beach while the incoming tide of ‘Science’ mounts higher and higher corresponds to nothing in my own experience. That grand myth … is not for me a hostile novelty breaking in on my traditional beliefs. On the contrary, that cosmology is what I started from. Deepening distrust and final abandonment of it long preceded my conversion to Christianity. Long before I believed Theology to be true I had already decided that the popular scientific picture at any rate was false. One absolutely central inconsistency ruins it….

The whole picture professes to depend on inferences from observed facts. Unless inference is valid, the whole picture disappears. Unless we can be sure that reality in the remotest nebula or the remotest part obeys the thought laws of the human scientist here and now in his laboratory — in other words, unless Reason is an absolute — all is in ruins. Yet those who ask me to believe this world picture also ask me to believe that Reason is simply the unforeseen and unintended by-product of mindless matter at one stage of its endless and aimless becoming.

Here is flat contradiction. They ask me at the same moment to accept a conclusion and to discredit the only testimony on which that conclusion can be based. The difficulty is to me a fatal one; and the fact that when you put it to many scientists, far from having an answer, they seem not even to understand what the difficulty is, assures me that I have not found a mare’s nest but detected a radical disease in their whole mode of thought from the very beginning. The man who has once understood the situation is compelled henceforth to regard the scientific cosmology as being, in principle, a myth; though no doubt a great many true particulars have been worked into it.

After that it is hardly worth noticing minor difficulties. … More disquieting still is Professor D.M.S. Watson’s defence. ‘Evolution itself,’ he wrote, ‘is accepted by zoologists not because it has been observed to occur or … can be proved by logically coherent evidence to be true, but because the only alternative, special creation, is dearly incredible.’ Has it come to that? Does the whole vast structure of modern naturalism depend not on positive evidence but simply on an a priori metaphysical prejudice? Was it devised not to get in facts but to keep out God?

Even, however, if Evolution in the strict biological sense has some better grounds than Professor Watson suggests — and I can’t help thinking it must — we should distinguish Evolution in this strict sense from what may be called the universal evolutionism of modern thought. By universal evolutionism I mean the belief that the very formula of universal process is from imperfect to perfect, from small beginnings to great endings, from the rudimentary to the elaborate, the belief which makes people find it natural to think that morality springs from savage taboos, adult sentiment from infantile sexual maladjustments, thought from instinct, mind from matter, organic from inorganic, cosmos from chaos. This is perhaps the deepest habit of mind in the contemporary world.

It seems to me immensely unplausible, because it makes the general course of nature so very unlike those parts of nature we can observe. You remember the old puzzle as to whether the owl came from the egg or the egg from the owl. The modern acquiescence in universal evolutionism is a kind of optical illusion, produced by attending exclusively to the owl’s emergence from the egg. We are taught from childhood to notice how the perfect oak grows from the acorn and to forget that the acorn itself was dropped by a perfect oak. We are reminded constantly that the adult human being was an embryo, never that the life of the embryo came from two adult human beings. We love to notice that the express engine of today is the descendant of the “Rocket”; we do not equally remember that the “Rocket” springs not from some even more rudimentary engine, but from something much more perfect and complicated than itself — namely, a man of genius. The obviousness or naturalness which most people seem to find in the idea of emergent evolution thus seems to be a pure hallucination.

On these grounds and others like them one is driven to think that whatever else may be true, the popular scientific cosmology at any rate is certainly not. …

I was taught at school, when I had done a sum, to “prove my answer.” The proof or verification of my Christian answer to the cosmic sum is this. When I accept Theology I may find difficulties, at this point or that, in harmonising it with some particular truths which are imbedded in the mythical cosmology derived from science. But I can get in, or allow for, science as a whole. Granted that Reason is prior to matter and that the light of the primal Reason illuminates finite minds, I can understand how men should come, by observation and inference, to know a lot about the universe they live in. If, on the other hand, I swallow the scientific cosmology as a whole, then not only can I not fit in Christianity, but I cannot even fit in science. If minds are wholly dependent on brains, and brains on biochemistry, and biochemistry (in the long run) on the meaningless flux of the atoms, I cannot understand how the thought of those minds should have any more significance than the sound of the wind in the trees.

And this is to me the final test. This is how I distinguish dreaming and waking. When I am awake I can, in some degree, account for and study my dream. The dragon that pursued me last night can be fitted into my waking world. I know that there are such things as dreams; I know that I had eaten an indigestible dinner; I know that a man of my reading might be expected to dream of dragons. But while in the nightmare I could not have fitted in my waking experience. The waking world is judged more real because it can thus contain the dreaming world; the dreaming world is judged less real because it cannot contain the waking one. For the same reason I am certain that in passing from the scientific points of view to the theological, I have passed from dream to waking. Christian theology can fit in science, art, morality, and the subChristian religions. The scientific point of view cannot fit in any of these things, not even science itself. I believe in Christianity as I believe that the Sun has risen, not only because I see it, but because by it I see everything else.”