105c9—dl2. Soul is here specified as the reason for body's being alive (c9—11). Cebes does not balk at this. Presumably, it fits his own conception of soul as 'making' body. See on 87d3—e5.
Burnet's text, which gives 'soul' without the article throughout 105cll—e6, has been followed, although the MSS. vary on this point at 105d3, dlO, e4, and e6. 'Soul' without the article may mean 'soul-stuff rather than individual soul. See on 64e4—65a3 (p.89). Some commentators have wished to understand it, rather, as the Form of Soul, as at B6 in Version B given in the note on 104c7-d4 (p.204). The difficulties to which this leads may be illustrated from G. Vlastos's account of the context (P.R. 1969, 317-20).
Vlastos interprets the inference pattern established by the preceding examples as: 'x is F because, being A, it must participate in the Form A; and since the Form A entails the Form F, x must also participate in the Form F, and hence x must be F.' (His variables have been adapted to the conventions followed in these notes, where F and G are used for the Forms of opposites, and A for the Form of a non-opposite). Vlastos does not discuss the application of this formula to the argument for immortality. But it is clear that an argument of the proposed pattern could not prove the immortality of the soul in the way required by the present text. For applying the formula, we should have either:
(1) 'A soul is alive because, being a soul, it must participate in the Form Soul, and since the Form Soul entails the Form Life, a soul must also participate in the Form Life, and hence a soul must be alive.'
or (2) 'A body is alive because, being besouled [or being a soul] it must participate in the Form Soul, and since the Form Soul entails the Form Life, the body must also participate in the Form Life, and so must be alive.'
But neither (1) nor (2) is satisfactory. (1) will not fit the text, for it ignores the soul's relationship to the body, which cannot be eliminated, even if the 'subtle' answers of 105b—d are taken as Forms (see previous note). And (2) clearly does not yield the conclusion for which Socrates wishes to argue. He needs a conclusion not about body but about soul. Moreover, he needs a conclusion not just about the Form of Soul, which is 'immortal' like any other Form, but about a particular soul. Yet if the reference at 105c9—d5 is to the Form of Soul, it is hard to see where or how the transition to particular soul, or soul-stuff, is supposed to occur. In Version B a transition has been effected at 105dl0—11, by taking those lines to mean that an individual soul will never admit the opposite of what is imparted by the Form of Soul to the body (step B8). But this reading is factitious, and not warranted by anything in the text.
Note also that the words 'Then soul, whatever it occupies, always comes to that thing bringing life' (d3—4) seem intended as an inference from 105cl 1—d2. So if the earlier lines refer to the presence of particular soul, or soul-stuff, in the body, it is natural to take 105d3—4 in the same way.
It is therefore preferable to take the whole of the present passage as referring to a particular soul, or soul-stuff, whose presence in a body quickens it, as in Version A. Whether or not Platonic ontology recognizes a Form of Soul, parallel to the Form of Three at 104d5— 6, and despite the parallelism of language with that passage, a more coherent argument emerges if such a Form is not read into the present text.
On either of the versions distinguished, the main principle of the argument is vulnerable. On Version A, the critical point is the claim that items 'bringing' an opposite F to whatever they enter will not admit G. Since this principle (A5 in the summary at 104c7-d4) depends upon the 'definition' at A4, the argument is flawed by defining the entities in question as those that 'bring' the Form F to whatever they enter. It may, of course, be simply stipulated that no x shall count as a 'reason' for _y's being F unless x is itself un-G. But if this artificial restriction is to be imposed upon the concept of a 'reason', it has to be asked whether there might, for some values of F, simply be no 'reason' for things' being F that meets so stringent a condition. See previous note (p.213).
On Version B, the core of the argument will be (B6—B9) that since any body occupied by the Form Soul must be alive, no individual soul can ever admit death. The mainspring of this inference will be the principle (B3) that TV-instances of a Form A will not admit the opposite of a property F imparted by that Form to its ^-instances. But this too seems questionable. For TV-instances may, perhaps, be qualified by the opposites of the properties their Forms impart. An individual hemlock plant, an TV-instance of the Form Hemlock, may be living, even though jT-instances occupied by the Form of Hemlock (i.e. bodies sufficiently dosed with hemlock) must be dead. This example may seem contrived. But the conception of the Form of Soul's occupancy of a body (B6) is itself both artificial and opaque.
105dl3—e9. It is now argued that since soul will never admit the opposite of the Form that it brings, i.e. the Form of Life, it will not admit death, and must therefore be 'im-mortal'.
At 105dl6—el the words rendered by their derivatives, 'musical' and 'un-musical', have the broader sense of 'cultured' and 'uncultured' (see on 60c8—61cl). 'Un-musical' and 'un-just' are used, like 'un-even' (dl5), for verbal symmetry with 'im-mortal'. Similarly, at 106a3—10 'un-hot' and 'un-coolable' translate words coined by Plato to parallel 'im-mortal'. It is important to take these predicates as meaning not merely 'not being G' but 'never being G' or 'incapable of being G\ This is the point of inferring 'is un-G' from 'does not admit the Form G'.
Failure to take note of this has sometimes led to charges of equivocation upon the word for 'immortal'. Thus, D. Keyt has argued (Phronesis 1963, 170—1) that in the present passage it means merely 'not dead', or 'alive', whereas by 106e5—6 it has come to mean 'never dying'. But this disregards the force of 'doesn't admit death', from which 'im-mortal' is derived at 105e2—3. To say that a thing does not 'admit' G means that it will never, while remaining itself, participate in that Form. Cf.l02e, 103d, 104b-c, 105a, and note the emphatic construction translated 'will absolutely never admit', at 105dl0—11. It follows that the predicate 'im-mortal' means not merely 'is not dead' but 'will never be dead'. There is, therefore, no shift in the meaning of 'immortal'. It means consistently 'never dying' or 'incapable of dying'. See also on 64c2—9 (p.87), 72e7—73a3 and 95b5-e6.