Lewis’ theology of creation is quite robust but he has been the object of some criticism for being somewhat sympathetic to evolution. Of course, Lewis does not believe in what he calls ‘Evolutionism’ but he also has no issue with accepting evolution as a scientific theory. Lewis wrote a short article that helps make sense of his views:
The central idea of the Myth is what its believers would call ‘Evolution’ or ‘Development’ or ‘Emergence,’ just as the central idea in the myth of Adonis is Death and Re-birth. I do not mean that the doctrine of Evolution as held by practicing biologists is a Myth. It may be shown, by later biologists, to be a less satisfactory hypothesis than was hoped fifty years ago. But that does not amount to being a Myth. It is a genuine scientific hypothesis. But we must sharply distinguish between Evolution as a biological theorem and popular Evolutionism or Developmentalism which is certainly a Myth.
Elsewhere Lewis goes to great lengths to articulate that while he believes that the theory of evolution can be a helpful tool for understanding the universe, it is also just that—a tool. He highlights this truth in order to recognize that science can often help us understand the creation, but is not, by itself, sufficient to build an entire worldview.
Science is philosophically built upon empiricism and empiricism is a terribly shaky foundation for one’s epistemology. Empiricism claims that objective knowledge comes through observation and this claim drives many objections against the miraculous accounts that we find in the Bible. The reasoning goes that since we cannot repeat and observe, say the parting of the Red Sea, then there is no way to know if the account in Exodus is actually true. This sounds like a powerful objection to God’s supernatural power but upon further reflection it is nothing but folly (Pr. 18:2).
The whole premise of empiricism is that we must be able to observe and repeat events to determine if they are true but this leaves men in the great place of uncertainty. Since man is a finite creature, he can never exhaustively observe every variable, which means that his theories are perpetually subject to contradiction. That is to say, every theory built solely upon observation is always hanging on the cliff of uncertainty. We need a standard to interpret our observations and the only certain and infallible standard is the Word of God.
C.S. Lewis does not come to this conclusion but he does want to explore why scientific knowledge is possible. Lewis argues that if the universe is understood through intelligence then the most probable explanation is that the universe must have been created by an intelligent designer. Lewis makes some compelling points here but I would go one step further and say that God’s existence is not merely probable, but rather, that science, intelligence, and knowledge are all impossible without God since God is the very source and fountain of all knowledge (Ro. 11:33-36).
 Evolutionism is essentially the Naturalist worldview.
 Lewis, Signature Classics, 171.
 Barbieri, Fabio Paolo. “CS Lewis: The Funeral of a Great Myth (for the debate on atheism as religion).” (April 8, 2009). Accessed August 17, 2016. http://fpb.livejournal.com/297710.html,.
 Lewis, Signature Classics, 29.
 Epistemology is the study of knowledge.