C. S. Lewis regularly argued that naturalism is self-defeating. On a naturalistic account, reasons are only accidental because beliefs are caused. Here is a version of the argument from his allegorical autobiography.


IN THE WARMTH of the afternoon they went on again, and it came into John’s mind to ask the lady the meaning of her second riddle.

‘It has two meanings,’ said she, ‘and in the first the bridge signifies Reasoning. The Spirit of the Age wishes to allow argument and not to allow argument.’

‘How is that?’

‘You heard what they said. If anyone argues with them they say that he is rationalizing his own desires, and therefore need not be answered. But if anyone listens to them they will then argue themselves to show that their own doctrines are true.’

‘I see. And what is the cure for this?’

‘You must ask them whether any reasoning is valid or not. If they say no, then their own doctrines, being reached by reasoning, fall to the ground. If they say yes, then they will have to examine your arguments and refute them on their merits: for if some reasoning is valid, for all they know, your bit of reasoning may be one of the valid bits.’

–C. S. Lewis, The Pilgrim’s Regress (pp. 62-63).