To: Matthew M.
From: Geoffrey Klempner
Subject: Plato's arguments for the immortality of the soul
Date: 6th January 2011 11:24
Thank you for your email of 26 December, with your essay for the University of London BA Plato and the Presocratics module, in response to the question, 'Does either (a) the affinity argument or (b) the final argument succeed in proving the immortality of the soul? If not how does it fail?"
Your essay contains some useful discussion of the relation between Plato's theory of Forms and his arguments for the immortality of the soul. As you point out, we have to grant Plato a number of premisses -- not least, the existence of the Forms -- before his argument even gets off the ground. However, I think that your answer to this question could be improved.
First, the most obvious point, if an examiner invites you to either look at argument (a) or look at argument (b) then the 'either...or' is understood in an exclusive sense, 'either... or, but not both'. By contrast, in formal logic, the connective 'v' (Latin 'vel') means, 'either... or... or both', i.e. the inclusive sense of or. This is not a picky point. You won't get extra credit for giving the examiner more than you were asked for!
To be fair, you do make the point that Plato's final argument depends on the previous argument from affinity. (I say more about this below.) So it would be relevant to discuss this dependence. However, it is not until the second paragraph on page 2 that you finally get down to doing what you said you were going to do, i.e. assess the validity of the final argument.
My second criticism, however, is that you miss the invalid step in Plato's proof. I'm stating this somewhat dogmatically, but it is one of those cases (comparatively rare in textual exegesis of Plato) where Plato does appear to commit a blatant non-sequitur.
The soul is the principle of life. As such, it does not 'admit' the opposite of life, i.e. death. Whereas a human body can be alive or dead. But what exactly does this mean? Being alive, for a human being, is having a soul, an active, fully functional life principle. On death, the soul departs and the body ceases all activity.
If someone suggested that a soul could die, this would be nonsensical -- or at least lead to an infinite regress -- as it would assume that the soul itself possesses its own life principle, the 'soul of a soul' which can depart, leaving behind a 'dead soul'.
So far, so good. But what exactly does that mean? When I die, my soul will depart from my body. My soul cannot die (because it doesn't have 'the soul of a soul'). It is the very principle of life. However, the one thing that Plato hasn't proved is that the 'deathless', that which is incapable of death because it is the principle of life, is incapable of being destroyed. He simply asserts it.
It would be fully consistent with what Plato says about the nature of the soul and the way it brings life to the body, to hold that the soul itself can puff out of existence any time, not dying in the way a body dies, by 'losing its principle of life' but simply by instantaneous obliteration. If it happens to be in the body at the time, then the body dies, but the soul can also be destroyed after it has been separated from the body. In other words, the only advantage of having a soul is that we face the prospect of ceasing to exist, twice.
Of course, Plato has an answer to this, but to get that answer we do have to look at his previous arguments, in particular the argument that the soul is 'like' the forms. (You make the point that the final argument depends on the affinity argument, but you don't specifically identify the gap in the final argument that the affinity argument purportedly fills.) The soul cannot be destroyed because it is like the forms, and the forms are eternal and indestructible. But, as you say, this is a weak argument because it doesn't follow from the fact that the soul is 'like' the forms in some respects, that it is like the forms in the crucial respect of being eternal.
You will sometimes see variations on this question such as, ''In the Phaedo Plato is concerned to prove the indestructibility of the soul, not its immortality.' Discuss.' It is fair to say that the dramatic form of the Phaedo obscures Plato's purpose somewhat. One can be reasonably confident that if this question was discussed in the Academy, then the need to fill the gap in the final argument would have been well understood.
All the best,