EPISTEMOLOGY experience of the heavens, and only after mastering astronomical phenomena they go on to seek causes and oVer proofs A similar method should be adopted in the life sciences (APr 1 639b7–10, 640b14–18) Science begins, but does not end, with experience, and, like Plato, Aristotle has an elaborate classiWcation of cognitive and intellectual states Both philosophers regard moral virtue and intellectual excellence as two species of a particular genus; but whereas Plato (no doubt under the inXuence of Socrates) tended to treat virtue as if it was a special kind of science, Aristotle treats science as a special kind of virtue The Aristotelian counterpart of Plato’s anatomy of knowledge occurs in one of the common books of the Ethics (NE 6, EE 5) where he is dealing with intellectual virtues The Greek word ‘arete’ corresponds to both ‘virtue’ and ‘excellence’; so I shall leave it, in the present context, untranslated The nature of the arete of anything depends upon its ergon, that is to say its job or characteristic output The ergon of the mind and all its faculties is the production of true and false judgements (NE 1139a29) That, at least, is its ergon in the sense of its characteristic activity, its output whether it is working well or ill; its activity when it is working well and doing its job, and therefore its ergon in the strict sense, is truth alone (2 1139b12) The intellectual aretai, then, are excellences that make an intellectual part of the soul come out with truth There are Wve states of mind that have this eVect—techne, episteme, phronesis, sophia, nous—which we may translate as skill, science, wisdom, understanding, and insight (3 1139b16–17) Skill and wisdom are both forms of practical knowledge: knowledge of what to and how to bring things about Skills, such as architecture or medicine, are exercised in the production (poiesis) of something other than their exercise, whether their output is concrete, like a house, or abstract, like health Wisdom, on the other hand, is concerned with human activity (praxis) itself rather than with its output: it is deWned as a ratiocinative excellence that ascertains the truth concerning what is good and bad for human beings (4 1140b5, b21) It is characteristic of the wise man to deliberate well about goods attainable by action: he is not concerned with things that cannot be other than they are (7 1141b9–13) Thus wisdom diVers from science and understanding, which are concerned with unchanging and eternal matters The rational part of the soul is divided into two parts: the logistikon that deliberates and the epistemonikon that is concerned with the eternal 164