Exorcising the Cartesian demon

Since Roger Olson trotted out the issue of Cartesian demons in reference to Calvinism, I’ll say a little more about it. The Cartesian demon is one of those sceptical thought-experiments like the brain-in-the-vat.

But a fundamental problem with this thought-experiment is that it’s ultimately otiose. An exercise in self-stultifying futility. Suppose the argument is successful. Then what?

Suppose I might be living in a complete, unfalsifiable illusion? Well, since, ex hypothesi, there’s nothing I can do in that situation to break the spell, I have no choice but to go right on living in my illusion as if it’s real. The thought-experiment gives me no alternative. 

So what does the thought-experiment accomplish? It’s not something I can act on. For its truth or falsity is empirically equivalent. The Cartesian demon is consistent with my being an atheist, idealist, Calvinist, Confucian, Arminian, Mambo, headhunter, or what have you. You can plug every conceivable position into the Cartesian demon, which translates every claim and counterclaim into the identity of indiscernibles.

Either the hypothetical is true or false. If true, there’s nothing I can do to disprove it, so it has no impact on what I think or do one way or the other. If true, it makes no difference what I think of the Cartesian demon.

The illusion is indetectible, so I’m condemned to live the same way whether it’s true or false. But if it’s false, then I don’t need to disprove it since, in that event, I’m not trapped in an illusion.

If it’s true, I can’t disprove it–but if it’s false, I don’t have to. Therefore, the Cartesian demon is a thought-experiment I can ignore with total equanimity. Nothing gained, nothing lost.