Keyt interprets 'soul doesn't admit death' at 105e4 as 'nothing can at one time possess a soul and be dead', and then objects (op.cit. 171) that in order to get his desired conclusion Plato must subsequently shift the predicate 'immortal' from that which has soul to soul itself. But this reading of 'soul doesn't admit death', which stems from construing 'soul' at 105d3—5 as an'immanent Form', is unnatural. If 'soul' is not taken as immanent Form, but as particular soul, or soul-stuff, then the predicate 'immortal' can readily attach to soul itself at 105e6, and no shift of subject need be supposed.
The charge of equivocation upon 'immortal' is related to another, often repeated criticism. The argument proves, it has been objected, only that soul is not dead 'whenever it exists' or 'while it is still soul' or 'so long as it is': it does not prove that soul is not at any time dead, and so not-dead or 'immortal' in the required sense. D. O'Brien (C.Q. 1967, 229-31) suggests that Plato may think he is entitled to omit the qualification 'whenever it exists', in virtue of his contention that soul is 'always', i.e. necessarily or essentially, alive. But it seems more likely that he was aware of the need for proof of the existence of a subject of the required type, and that this is precisely what gives rise to the attempted proof of soul's 'imperishability' at 106a—e. See next note (p.217). At Euthydemus 296a—d it is noticed that 'always' is logically treacherous, and that 'whenever' clauses may not safely be dropped after its occurrence.
The concept of immortality is not, however, without difficulty. For what is meant by the 'death' which soul will not admit? It cannot here mean 'separation from the body', for soul will admit 'death' in this sense (see on 64c2—9, p.87). Could it mean 'perishing'? This is also difficult, for two reasons, (i) Death has just been said to be the opposite of Life (d6—9), and must therefore be thought of here as a state rather than as an event, whereas 'perishing' is an event, (ii) If 'death' means 'perishing', what is to be made of the claim that soul is immortal and imperishable, and of the coming argument for the latter predicate? It is, in fact, hard to understand 'death', and 'immortal', in such a way that the final page of the proof is neither otiose nor question-begging. Related difficulties about the meaning of 'death' will arise at 106bl—4 and 106e5—7.
105el0—107al. This section contains the final phase of the argument. Its purpose is to distinguish the case of soul from those of snow, fire, and three, to which it has so far been assimilated. In those cases, the possibility of 'perishing', in face of ail attack by the excluded opposite, remained open. But in the case of soul, this possibility is to be ruled out; soul is not only immortal, it is also imperishable.
The point of contrasting soul with the other cases is to fill a gap in the proof of immortality expressed by Hackforth as follows (163): 'what has been shown is that the predicate "deathless" is contained in the meaning of the subject, soul; whenever, therefore, this subject exists, it has this predicate: but to show that the subject always does exist is quite another matter.' See the criticism of Strato of Lampsacus, given by Hackforth, 196 (g) and (m), and previous note. The present phase of the proof is meant to forestall such criticism. It tries to move beyond the tautology 'as long as a soul exists, it is not dead' to the claim that soul does, indeed, always exist. Like the Ontological Argument, it seeks to conjure an existential proposition out of a conceptual analysis. This is the reason for insisting upon 'imperishable' as an additional predicate (cf.88b6,95cl, and see on 88al-b8,95b5-e6).
In outline the argument runs as follows:
If the immortal is imperishable, soul will be imperishable
(c9—dl).
The immortal is imperishable (d2—9).
So
Soul is imperishable (el—107al).
There are uncertainties of interpretation at each of these stages.
1.(1) Does 'the immortal' mean (i) 'that which is immortal', or (ii) 'the property of being immortal'? For (i) see D. O'Brien, C.Q. 1967, 207. For (ii) see D. S. Scarrow,P.R. 1961, 245-52. With© the argument will be that since whatever is immortal is imperishable, the soul, being immortal, must be imperishable as well. With (ii) the argument will be that since the property of being immortal is imperishable, its bearer must be imperishable as well.
(ii) is a possible reading, if 'the immortal' is construed as parallel with 'the odd'. For 'the odd' is used at 106b5—6 in a manner parallel to 'the hotness in the fire' (b6—7). At 106b7—8 also it means 'oddness' rather than 'that which is odd', for at 106c5, which looks back to 106b7—8, the meaning must be 'oddness and three depart and go away'. But against this reading of 'the immortal': (a) It is far from clear that 'the im-mortal' is being used in a manner parallel to 'the odd'. Formally, it is parallel, rather, to 'the un-even', the 'un-hot' and 'the un-coolable'. These probably mean 'that which is un-G' rather than the property 'un-Gness'. (b) 'The immortal is also imperishable' at 106b2 and 106c 10 (cf.el) seems more likely to mean 'that which is immortal is also imperishable'. For on this view, the point of 'also' will be that the subject is imperishable as well as immortal, whereas on the alternative view 'also' has no clear function at all. (c) At 106e6 the phrase translated 'the immortal part' must mean 'that which is immortal', since it alludes directly to the soul. Scarrow's reading would therefore involve a shift at some point in the meaning of 'the immortal'. And (d) the allusion to God and the Form of Life (d5—9) would remain, on this view, as a rather lame pendant to the argument.
The references to 'death' at 106b3 (cf.e5) raise several problems: (a) 'Death' can hardly be understood here either as (i) 'separation of soul from body' (64c2—9), or as (ii) 'perishing of soul' (91d6—7). Clearly, in the words 'it won't admit death nor will it be dead', 'death' cannot be understood in sense (i). For the soul does 'admit death' in that sense of 'death', when it is separated from the body (see III below). O'Brien (C.Q. 1968, 101, n.2) suggests that (ii), which he takes to be a redefinition of 'death', enables 'nor will it be dead' (b4) to mean 'nor will it cease to exist'. But this is not satisfactory either. For Socrates is here recalling the conclusion of 105e2—7, that soul is immortal. Since this conclusion is a premiss in his present argument for its imperishability, he could not use the words 'nor will it be dead' to mean 'nor will it cease to exist', without assuming exactly what he is trying to prove.
Both here and at 106e5—7 it is difficult to interpret the notion of death's 'attack'. Note the difference between this and the impact of hot and cold upon snow and fire at 106a. It is not the opposites themselves, hot and cold, that are said to attack snow and fire, but something characterized by those opposites. But there is no embodiment of death in something that is 'applied' to the soul, or to the man, as something hot or cold is physically applied to snow or fire (106a4, a9).
Did Plato postulate a Form of Death? Although such a Form seems required by the framework established for the argument, Socrates nowhere speaks of one in so many words. A Form of Death, unfortunately, generates an awkward paradox. If included in the Form-world as characterized earlier (79d2, 80bl, 81a5), it would have to be immortal or 'deathless'. But a deathless Form of Death would seem to infringe the basic principle of the present argument, that no Form will admit its own opposite.