METAPHYSICS points substances? Are numbers substances? But he addresses right away, though in a roundabout manner, the great Platonic question: Are there separate substances of any kind, distinct from those we can perceive with our senses? (F 1028b8–32) Essence and Quiddity We saw that in the Parmenides Plato introduced a form of predication per se: S is P per se if being P is part of what it is to be S Aristotle is keenly interested in this form of predication In the Categories it is predication in the category of (second) substance In the Metaphysics it is predication that answers the question what kind of thing something is (ti esti) Sometimes Aristotle speaks of the ‘what-is-it?’ of a thing; and in the context of the present discussion he often uses an almost untranslatable expression, to ti en einai, composed of the deWnite article, the question ‘what-is-it?’ and the inWnitive of the verb ‘to be’ This translates literally as ‘the whatis-it to be’ of a thing, i.e the type of being that answers the question ‘What is it?’ Latin commentators on Aristotle sometimes used the word ‘quidditas’ to correspond to this Greek expression; the Latin question ‘Quid est?’ corresponds to the Greek question ‘Ti esti’ Many English scholars use ‘essence’as a translation That is quite possible; but I shall take my cue from the Latin and use the word ‘quiddity’ ‘Essence’ is, of course, itself a Latinism, deriving from the Latin verb for being, ‘esse’, just as the Greek ‘ousia’ derives from the Greek word for being There is good reason, however, to stick with the traditional translation ‘substance’ for ‘ousia’ We can then use the word ‘essence’ to cope with another crabbed Aristotelian construction We can speak, for example, of the essence of gold where Aristotle would speak of ‘the for-gold being’, using the inWnitive after the Greek dative case, meaning ‘what it is for gold to be gold’ This last construction, again, is descended from Plato’s concern with questions about what is and what is not part of what being gold involves For most purposes, ‘quiddity’ and ‘essence’ can be treated as synonyms With these preliminaries, we can state the agenda that Aristotle sets for himself at the beginning of the central section of Metaphysics F ‘Substance’, he says, has four principal meanings: the quiddity, the universal, the genus, 218