 A great barrier to correct thinking is language itself, which, because it has a name for death, may suggest that death (being dead) is something a person can experience and hence deserves to be feared. Words must be understood in their basic sense, Epicurus says, as opposed to what he calls “empty sounds” (LH 37). The culprit in misunderstanding is always an illegitimate inference from sensation (the latter including thoughts produced by film-like images). An example is the belief that centaurs exist. Epicurus does not deny that the thought of a centaur corresponds to some real stimulus in the form of simulacra: his theory of knowledge commits him to the view that it must. But the flimsy laminas as they float through the air can become distorted or interfere with one another, and thus the upper part of a human figure may get loosely attached to the lower part of a horse’s. We know that this is unreal because such a combination is physically impossible: horses and human beings mature at different rates, for example, and eat different foods (see Lucretius 5.878–91; cf. Palaephatus On Incredible Tales 20). Beliefs about whether sensations correspond to an actually existing thing must be tested against knowledge of the world, as informed by Epicurean theory.