Discussing philosophical skepticism in his new book, Freedom & Neurobiology, John Searle:

Go to any university bookstore and look at the section on, for example, molecular biology or mechanical engineering, and you will find an accumulation of knowledge, the sheer volume of which would have taken Descartes� breath away. It is hard to send men to the moon and bring them back and then take seriously the problem, for example, whether the external world really exists. This is not to say that there is no room for skeptical epistemology in philosophy, but I regard the epistemic puzzles as I regard Zeno’s paradoxes about space and time. It is an interesting paradox how it is possible for me to move across the room. First I have to go half way, and then prior to that, half of that half, and prior to that half of that half, and so on. And similarly, it is an interesting puzzle how I can have certain, objective, and universal knowledge given the various skeptical possibilities that one can raise. But, all the same, we do not seriously think that Zeno’s paradoxes show that space and time do not exist, nor do most of us suppose that the skeptical paradoxes cast any doubt on the existence of knowledge.