 The ability to reason or calculate (logismos) cannot be a function of images. It is the faculty that lets us infer by analogy from the visible world to the invisible, and also that with which we may recognize that not all pleasures are to be chosen at all times, since some immediate pleasures may lead to long-term pain or harm (Letter to Menoeceus = LM 129). What is more, one must know something about the nature of pleasure in order to pursue it rationally, and likewise for pain. Epicurus, it appears, uses the terms pleasure and pain (hêdonê, algêdôn) strictly in reference to physical pathê or sensations, that is, those that are experienced via the non-rational soul that is distributed throughout the body. As for the rational part or mind, we have positive and negative experiences through it too. Most prominent among the negative mental states is fear, above all the fear of unreal dangers, such as death. Death, Epicurus insists, is nothing to us, since while we exist, our death is not, and when our death occurs, we do not exist (LM 124–25); but if one is frightened by the empty name of death, the fear will persist since we must all eventually die. This fear is one source of perturbation (tarakhê), and is a worse curse than physical pain itself; the absence of such fear is ataraxy, lack of perturbation, and ataraxy, together with freedom from physical pain, is one way of specifying the goal of life, for Epicurus.