 It is widely believed that states of affairs that are truly mind-independent do engender radical skepticism. The skeptic contends that for all we could tell we could be brains in a vat—brains kept alive in a bath of nutrients by mad alien scientists. All our thoughts, all our experience, all that passed for science would be systematically mistaken if we were. We’d have no bodies although we thought we did, the world would contain no physical objects, yet it would seem to us that it did, there’d be no Earth, no Sun, no vast universe, only the brain’s deluded representations of such. At least this could be the case if our representations derived even part of their content from links with mind-independent objects and states of affairs. Since realism implies that such an absurd possibility could hold without our being able to detect it, it has to be rejected, according to anti-realists.