Reality+: Virtual Worlds and the Problems of Philosophy

by David J. Chalmers

Like me, Bouwsma thinks that the subject in Descartes’s evil-demon scenario is not undergoing an illusion. His reasons differ from mine, however. Bouwsma thinks that an illusion is an illusion only if it can be discovered. If an illusion cannot be discovered, as in Descartes’s evil-demon scenario, it’s not an illusion at all, and it’s not a deception. More precisely, Bouwsma’s evil demon can discover the illusion, but his subject, Tom, cannot. So when the demon says, “This is an illusion,” he’s correct, but if Tom were to say this, Tom would be wrong. For similar reasons, what Tom experiences counts as a “flower” for Tom but not for the demon. Consequently, when Tom says, “That’s a flower,” he’s correct. Bouwsma’s reasoning here is grounded in a sort of verificationism, which says that all meaningful claims are verifiable. You’ll recall that earlier we discussed the verificationism of Rudolf Carnap and other logical positivists, who held that skeptical hypotheses are unverifiable and therefore meaningless. Bouwsma takes a related line. He thinks that the hypothesis that there’s an illusion is meaningless if it cannot be verified. If we can never verify that the evil-demon scenario is an illusion, it’s not an illusion at all.