Argument from Reason?

[Angrboda]

One absolutely central inconsistency ruins [the naturalistic worldview].... The whole picture professes to depend on inferences from observed facts. Unless inference is valid, the whole picture disappears.... [U]nless 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.
—C. S. Lewis, "Is Theology Poetry?", The Weight of Glory and Other Addresses

More precisely, Lewis's argument from reason can be stated as follows:

1. No belief is rationally inferred if it can be fully explained in terms of nonrational causes.

I would proffer the following formulation:

1. Evolution is not rational.
2. Therefore, products of evolution are not rational.
3. We are rational.
4. Therefore, we are not products of evolution.

There's a fallacy of division in #2 that the parts of something have the same properties as the whole.