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The One and The Many: Aristotle on The Individuation of Numbers*

  • S. Gaukroger (a1)


In Book K of the Metaphysics Aristotle raises a problem about a very persistent concern of Greek philosophy, that of the relation between the one (τ⋯ ἓν) and the many (τ⋯ πλ***θ***), but in a rather peculiar context. He asks: ‘What on earth is it in virtùe of which mathematical magnitudes are one? It is reasonable that things around us [i.e. sensible things] be one in virtue of [their] ψνχ⋯ or part of their ψνχ⋯, or something else; otherwise there is not one but many, the thing is divided up. But [mathematical] objects are divisible and quantitative. What is it that makes them one and holds them together?’ (1077 a 20–4).



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1 cf. Ross, W. D., Aristotle's Metaphysics (2 vols. Oxford, 1953), ii. 414.

2 Annas, J., Aristotle's Metaphysics Books M and N (Oxford, 1977), pp. 145–6.

3 It might be considered helpful, in the light of this, to employ different terms for Plato's and Aristotle's ‘noetic’ numbers, but I think there are advantages in maintaining the same term for the two. The main advantage derives from the fact that Aristotle, in his discussion of numbers, is often explicitly criticizing Plato with the aim of challenging Plato's conception of the ontological status of non-sensible numbers, rather than drawing a different distinction which cuts across Plato's. Their respective views of sensible numbers are essentially the same, Plato characterizing them as those numbers which have ‘visible and tangible body’ (Rep. 525d).

4 cf. Klein, J., Greek Mathematical Thought and the Origin of Algebra (Cambridge, Mass., 1968).

5 Of some importance here is the use of the γνὼμων, a geometrical configuration which is ‘fitted’ to formations of monads showing similarity of kind between these formations. For a discussion of figurate numbers and the γνὼμων cf. Heath, T. L., A History of Greek Mathematics (2 vols. Oxford, 1921), i. 7684, and his notes on Definition 16 of Book 7 of Euclid's Elements in his edition of The Thirteen Books of Euclid's Elements (3 vols. New York, 1956), ii. 287–90.

6 cf. Szab⋯, A., The Beginnings of Greek Mathematics (Dordrecht, 1978), pp. 257 f.

7 Considerable problems arise when the doctrine of particular substances is extended to cover inanimate substances, and the topic has been the subject of considerable debate. Much of the literature on the question is cited and discussed in Hartner, E. D.,‘Aristotle on Primary ΟΥΙΑ’, Arckiv för Geschichte der Philosophic 57 (1975), 120.

8 cf. Elders, L., Aristotle's theory of the One (Assen, 1961), pp. 65–7, for a detailed discussion of Aristotle's use of this expression.

9 Aristotle provides the same kind of account for infinity (Ph. Γ, 204 a 8–206 a 8), place (Ph Ph. Γ., 209b 1–210a 13) and time (Ph. A, 218b21–220a 26).

10 A good account of Aristotle's view of the role of noetic matter in geometry is given in Mueller, I., ‘Aristotle on Geometrical Objects’, Archiv für Geschichte der Philosophie, 52 (1970), 156–71.

11 I have defended this interpretation of the noetic matter of numbers in my Aristotle on Intelligible Matter’, Phronesis, 25 (1980), 187–97; it would take us too far from our main topic to enter into the details of the justification here.

12 This is the way in which numbers are usually notated in Greek arithmetic (cf. Books 7 to 9 of Euclid's Elements) and it is upon these line lengths that arithmetical operations are performed. In multiplication, for example, the product of two lines is a rectangle having those lines at its sides. This procedure places severe conceptual and computational constraints on Greek arithmetic as compared to the arithmetic developed from the seventeenth century onwards: cf. Mahoney, M. S., ‘The Beginnings of Algebraic Thought in the Seventeenth Century’, in Gaukroger, S. (ed.), Descartes: Philosophy, Mathematics and Physics (New Jersey, 1980).

13 This point is different from Aristotle's more specific remark at Metaph. I, 1053 b 25–1054 a 10, where he argues that ‘one’ has different uses in different categories. What we are concerned with here is the equivocality of ‘one’ as applied to two things of the same category (substance).

14 cf. Lambros, C. H., ‘Are Numbers Properties of Objects?’, Philosophical Studies, 29 (1976), 381–9. Lambros presents what is, I think, a good prima facie case against Frege; whether it is conclusive is a different matter altogether, and one that I shall not take up here.

* This paper owes a great deal to those who have commented on earlier drafts, particularly Professor A. A. Long and two anonymous referees.

The One and The Many: Aristotle on The Individuation of Numbers*

  • S. Gaukroger (a1)


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