Platonic arguments for the immortality of the soul

PHIL 20208
Jeff Speaks

November 28, 2006

Plato is the classical source of philosophical arguments for the immortality of the soul. By calling them ‘philosophical’ arguments I am distinguishing them from arguments which are based on empirical research, like research into near-death experiences, and from arguments which rely on premises taken from a particular religious tradition. We will discuss empirical and religious arguments later. (The line between these is not always sharp. Philosophical arguments can sometimes use premises known by experience, and religious arguments might rely on religious doctrines which can be supported by philosophical arguments which don’t themselves presuppose any religious doctrines.)

The reading from Plato is a selection from his dialogue the Phaedo, which is his eulogy to his teacher, Socrates, and recounts the last hours of Socrates’ life. The form of the part of the dialogue we read is a conversation between Socrates and his friends before his death, in which he tries to convince them that there is nothing to fear from the death.

One thing to keep in mind about these arguments is that they seem, in places, to presuppose a kind of dualist view of the self. You might think that this view of the self makes arguments for immortality unnecessary: if we are immaterial souls, isn’t it obvious that we must survive death? It’s important to see that even though belief in immortality is often linked with belief in the soul, that there’s no immediate route from the latter to the former. I.e., there’s no obvious contradiction in thinking that we are immaterial souls which cease to exist when our bodies do.

1 The argument from generation out of opposites

The first of Socrates’ arguments for immortality begins on p. 117:

“Let us see whether in general everything that admits of generation is generated in this way and no other — opposites from opposites, wherever there is an opposite ...Let us consider whether it is a necessary law that everything which has an opposite is generated from that opposite and no other source. For example, when a thing becomes bigger, it must, I suppose, have been smaller first before it became bigger?”

Socrates next observes that death is the opposite of life. So, if his principle holds, it seems as though

“the living have come from the dead no less than the dead from the living. But I think we decided that if this was so, it was a sufficient proof that the souls of the dead must exist in some place from which they are reborn.”

One interpretation of what’s going on here: if death and life are opposites, and if it follows from this that something could have come to be living only after first having been dead, then it seems that we must, in some sense or other, exist when dead. But this is what Socrates is trying to show.

A criticism of this argument, based on the distinction between coming to exist and acquiring a property. Maybe coming to life is the former rather than the latter; but the argument seems to depend on it being an instance of the latter.

2 The argument from recollection

Socrates’ second argument (pp. 120-128) is based on his theory of recollection. That theory was an explanation of how we can come to know the kinds of things that we can. One way to see the motivation for this theory is via the ‘paradox of inquiry’:

For any question, either you know the answer or you don’t. If you know the answer, then inquiry is unnecessary. If you don’t know the answer, you’ll have no way of recognizing the correct answer when it presents itself — for if you don’t know what the correct answer is, how will you distinguish it from false answers? So if you don’t know the answer, inquiry is impossible.

One might take this paradox to support the view that, as Cebes puts it (p. 120)

“what we call learning is really just recollection. If that is true, then surely what we recollect now we must have learned at some time before; which is impossible unless our souls existed somewhere before they entered this human shape. So in that way too it seems likely that the soul is immortal.”

A response to the paradox of inquiry for the case of empirical knowledge, e.g. finding out what is for dinner in South Dining Hall. Why this doesn’t carry over immediately to the case of ‘a priori’ knowledge not obtained by calculation.

A second, related argument for recollection: the example of Meno.

A third argument: our knowledge of qualities like ‘absolute equality’ (p. 124) which we do not observe by our senses to exist anywhere in the world around us.

3 The simplicity argument

This argument leads Cebes to respond,

“It seems that we have got the proof of one half of what we wanted — that the soul existed before birth — but now we need also to prove that it will exist after our death no less than before our birth, if our proof is to be complete.”

This leads Socrates to another argument for the immortality of the soul:

“We ought, I think, to ask ourselves this: What sort of thing is it that would naturally suffer the fate of being dispersed? For what sort of thing should we fear this fate, and for what should we not? When we have answered this, we should next consider to which class the soul belongs; and then we shall know whether to feel confidence or fear about the fate of our souls.


Would you not expect a composite object or a natural compound to be liable to break up where it was put together? and ought not anything which is really incomposite to be the one thing of all others which is not affected in this way?”

Socrates’ thought here seems to be this: if a thing is composite, then it can be destroyed by being separated into its parts; if we observe things being destroyed, this is usually how it goes. But if something is incomposite, and has no parts, then it cannot be destroyed by being resolved into its parts. But it seems that there’s no other way in which a thing could be destroyed. So, if the soul is incomposite, it is indestructible, and so can’t be destroyed by death.

Then the question is: is the soul composite, or incomposite?

Socrates asks: “Is it not extremely probable that what is always constant and invariable is incomposite, and what is inconstant and variable is composite?”

Socrates then contrasts things which are constant and invariable — like absolute equality and absolute beauty — with things which are not, like the concrete material things around us. He concludes that in general things which are invisible are constant and invariable, whereas things which are visible are inconstant and variable. But it looks like the body is visible whereas the soul is invisible; so it looks like the soul is more like those things which have been found to be constant and invariable. But if the soul is constant and invariable, and the body is inconstant and variable, the soul must be less likely to be destroyed by death than the body. But the body is not destroyed by death; so all the more so must the soul be destroyed by death.

To this argument, Simmias gives the following objection (p. 139):

“You might say the same thing about tuning the strings of a musical instrument: that the attunement is something invisible and incorporeal and splendid and divine, and located in the tuned instrument, while the instrument itself and its strings are material and composite and earthly and closely related to what is mortal. Now suppose that the instrument is broken, or its strings cut or snapped. According to your theory the attunement must still exist — it cannot have been destroyed; because it would be inconceivable that when the strings are broken the instrument and the strings themselves, which have a mortal nature, should still exist, and the attunement, which shares the nature and characteristics of the divine and immortal, should exist no longer ...You would say that the attunement must still exist somewhere ...Well, if the soul really is an adjustment, obviously as soon as the tension of our body is lowered or increased beyond the proper point, the soul must be destroyed, just like any other adjustment ...

Socrates responds to Simmias’ objection in two ways:

Cebes offers a different objection: even if the soul is less apt to be destroyed then the body, it does not follow that in every case the soul lasts longer than the body. A person’s body is less apt to be destroyed than a coat; but, even though I outlive most of my coats, it is clearly possible that at least one of my coats should outlive me. So why not say that, by analogy, it is possible that in at least some cases the soul is destroyed at death, even though the body remains? (pp. 141-2)

Socrates sketches a reply to Cebes based on the principle that nothing can both have a property and have the opposite property; for example, no collection of things can be both even and odd. Now note that there are some things which have a certain property essentially — e.g., the number three has essentially the property of being odd. So it follows that it is impossible for something that is three to have the property which is the opposite of oddness, namely evenness. Socrates thinks that it is an essential property of the soul to be alive. So, the soul cannot have the opposite property, which is being dead. So, the soul cannot die. So, the soul is destructible.

A problem with this argument based on the distinction between ceasing to exist and acquiring the property of being dead.

Another way of replying to Cebes is to emphasize Socrates’ earlier point that the soul is not just more like things which seem invariable, but also incomposite, and therefore indestructible. Why should we think that the soul is incomposite? Is it is true that incomposite things cannot be destroyed?