Problem
Suppose someone says, "It doesn't matter whether thick illusions are possible. The important thing is that we actually are sometimes taken in by illusions. Maybe they're only thin illusions, but it already follows by the Frequency Principle that we can never be completely certain that we're not under illusion." (i) Make the skeptical argument here explicit. (ii) What cognitive state does the argument target? (iii) Critically discuss and evaluate the argument.