[I]t is true that ‘I seem to see a table’ does not entail ‘I see a table’; but ‘I seem to feel a pain’ does entail ‘I feel a pain’. So scepticism loses its force—cannot open up its characteristic gap—with regard to that which ultimately most concerns us, pleasure and pain.

Galen Strawson, Freedom and Belief, Oxford, 1986, p. 223, n. 29