On the other hand, if fire and snow are not Forms, but physical stuffs, there need be no difficulty in understanding 'get out of the way' and 'perish' as genuine alternatives: snow can melt, and fire can be put out, or they can be moved. Their 'perishing' by being melted or quenched is expressly suggested at 106a3—10, and the idea of their 'getting out of the way' by being moved, although nowhere mentioned, is not hard to supply. Burnet therefore seems correct in saying (note on 104dl): 'it has not been suggested that fire and snow are Forms, and it seems improbable that they are so
regarded.'
At 103e2—5 Socrates generalizes from the snow and fire examples: certain things, although not identical with the Form F itself, always possess that Form's character. For the words translated 'form' and 'character' see on 65d4—e5 (p.93) and note 72.
What is meant by qualifying the generalization with the words 'in some cases of this kind' (e2)? Is it that (i) only for some, but not for all, of the opposite Forms mentioned, there are things other than those Forms that are always entitled to their name? On this view, it will be implied that for certain Forms, such as Large and Small, there is nothing corresponding to snow and fire, i.e. nothing that is always large, or always small, in the way that snow is always cold, and fire always hot. Alternatively, does Socrates mean that (ii) only some, but not all, stuffs are invariably characterized by one member of a pair of opposites? It will then be implied that certain stuffs, unlike fire and snow, may be characterized by either of a pair of opposites (at different times), and are not invariably characterized by one member of a pair only. _
'Some cases of this kind' is more naturally taken, as in (ii), to mean 'such things as fire and snow', than as meaning 'such Forms as Hot and Cold'. But what, on this view, would be ruled out by the reservation? O'Brien (op.cit. 211, n.2) suggests water, which may be either hot or cold, unlike fire, which can only be hot. But water is, arguably, always wet and never dry, and thus stands in the same relation to the Forms of Wet and Dry as does fire to the Forms of Hot and Cold. If the reservation is meant to exclude things that are not invariably characterized by any opposite, what would illustrate it? This question calls for further clarification of the concept of an 'opposite'. On a broad interpretation, it might be difficult to find examples of things that are not invariably characterized by some opposite or other. But the reservation would be pointless if its effect were to exclude an empty class.
103e5—104c6. A numerical example is now introduced. Three, while not itself an opposite, must always be characterized by one member of a pair, the Odd, and so must exclude the other, the Even. The argument is sometimes criticized here for assimilating numerical to physical examples. Thus, Hackforth (157) objects that snow's refusal to admit cold is 'a physical fact known through sense perception', whereas the corresponding truths about three and soul are 'statements about the implications of terms'. G. Vlastos (P.R. 1969, 321) speaks of 'Plato's reduction of physical to logical necessity in the Phaedo'. See also E. L. Burge, Phronesis 1971,11— 13. But the passage need not be read as embodying any doctrine about the nature of physical necessity. The fire, snow, and number examples may be taken as entirely subservient to the proof of immortality. For this proof, the vital point is not so much the assimilation of physical to logical necessity as the basing of metaphysical conclusions upon conceptual argument, the derivation of existential propositions about the soul from consideration of its essential nature. See on 105el0-107al (p.217).
It is true, however, that the numerical examples serve to bridge, and even conceal, a serious gap between soul and the physical stuffs with which it has so far been compared. Soul will be thought of as causally affecting bodies (105c—d), as imparting life to the bodies it occupies, just as fire and snow impart heat and cold. But this analogy is weakened by the fact that soul, unlike fire and snow, is not observable (79b7—15). Fire and snow can be recognized and observed independently of the bodies they occupy. Our knowledge that a body has fire or snow in it does not depend upon our finding it to be hot or cold. By contrast, the presence of soul in a body is not observable independently of that body's being alive. The life that we find in a body is our sole warrant for ascribing soul to it at all. Hence the notion of soul's 'bringing life' to body is not truly parallel with the other cases. The transition to it is helped by the example of three. For numbers, like the soul, are not sensible, nor are they observable independently of particular numbered sets.
The status of numbers in Plato is controversial. It is not clear whether he distinguished between the number n and the Form iV-ness. But the following considerations suggest the need for such a distinction: (a) When we speak of, e.g., 'four threes', or 'adding three and three', the threes mentioned can hardly be the Form Threeness, which is unique, (b) Forms are held to be 'incomposite' (78c), whereas numbers might be regarded as consisting of abstract units, and hence 'composite', (c) Forms cannot 'perish', whereas numbers are conceived as able to do so (104cl—3, 106al). (d) Numbers, unlike Forms, can have contrasted predicates in different relations, e.g. 'more' and 'less', 'double' and 'half'.
Aristotle ascribes to Plato a doctrine of mathematical entities 'intermediate' between Forms and sensible things. The worth of this evidence is disputed, and the doctrine is, at most, inchoate in the dialogues. But an intermediate status for numbers would suit the present parallel between three and soul, in view of the soul's own intermediate status between the Forms and the sensible world (78c— 84b). And the above objections to viewing numbers as (a sub-class of) Forms warrant asking, for each occurrence of 'three' or 'threeness' in the coming argument, whether a Form or a number is meant. See W. D. Ross, P.T.I. 65-7, 206-12, A. Wedberg, P.P.M.
122-35, J. M. Rist, Phronesis 1964,33-7,1. M. Crombie, E.P.D. ii. 440ff.
For the terms 'three' and 'threeness' see on 101b9—c9. Nothing can be inferred from Plato's terminology. Note, especially, the different locutions used for members of the odd and even number series at 104a4—b4. The casual shifting from 'threeness' and 'fiveness' to 'two' and 'four' in parallel contexts suggests that no systematic distinction is intended between the two types of terms. See also on 104d5-e6,104e7-105b4.
Hackforth (151, n.2, cf.156) argues from the use of'threeness' at 104c5 that'three' at 104cl must mean the immanent Form of Three. But it does not follow from the use of 'twoness' and 'threeness' at 104c5, as Hackforth supposes (151, n.l), that the whole paragraph 104b6—c3 is concerned with Forms. For if'twoness' and 'threeness' at 104c5 mean the numbers two and three, it could well be the number three of which it is said (cl—3) that it will 'perish' rather than become even. Moreover, the items exemplified by three are said (b9—10) not to admit 'whatever Form may be opposite to the one that's in them'. To speak of a Form's being 'in them' is to suggest that 'they' are not Forms themselves.
Whatever may be meant by 'three' or 'threeness', it is difficult to understand the 'military metaphors' in relation to this example. What is meant by the Form Even's 'attacking' three, and how should three's 'getting out of the way' and 'perishing' be understood? As before, it is preferable to take these as genuine alternatives if possible. See on 103cl0—e5 (p.198). Perhaps three's 'getting out of the way' could be understood in a manner analogous to the withdrawal of Simmias' Largeness in face of a comparison with Phaedo instead of Socrates. Three might be thought of as withdrawing from a set, when that set is viewed in terms of a different unit-concept: three 'withdraws' from three musicians when they are viewed as one ensemble; by contrast, it 'perishes' when a fourth member is added to their number. Cf. Parmenides 129c4—d6.