Philosophy

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LECTURE: Aquinas on the immortality of the soul

A full body amputation

In the previous lecture, we discussed why Aristotle and Aquinas think that the human intellect is immaterial – why they think that it is not a bodily organ, nor entirely dependent on any bodily organ. Let’s now talk about why Aquinas holds that this shows that the human soul is immortal.

Here’s an analogy that might help. A person or animal that loses a leg can, of course, still survive. An amputation need not be fatal. Even several amputations need not be fatal, however horrible. For example, if an animal lost all of its legs, its eyes and ears, and even some of its other organs, it might still be kept alive through extraordinary means.

But of course, if a non-human animal lost all of its bodily organs, it would not survive. There is nothing more to it than its bodily organs, so when they all go, the animal as a whole goes. Now, if human beings were like that – if everything about us was material or dependent on bodily organs – then we would be in the same boat. The death of the body would be the end of the person.

However, as we have seen, Aquinas thinks we are not like that. There is part of us – the intellect – that is not a material thing, not dependent on any bodily organ. Therefore, even when the entire human body dies, it does not follow that the person as a whole is destroyed. There is still a part that carries on – the intellect, which was never dependent on the body in the first place.

You might think of Aquinas’s view of death, then, as a kind of “full body amputation.” Needless to say, that’s a pretty serious amputation! But it is still just the removal of all of the bodily parts of a person – and not of all the parts, since the intellect is a part that is non-bodily.

The immortal soul

This means that the soul has, for Aquinas, a kind of natural immortality. Recall that the soul, as he conceives of it, is the substantial form of the living body. To be more precise, it is the substantial form of the human person – and the person is bodily, but only partly so.

Because the person is not entirely bodily, the person carries on in an incomplete way – reduced just to his or her immaterial intellect – after the body is gone at death. And because the person carries on (even if in an incomplete way), the soul, which is the substantial form of that person, carries on after death.

Aquinas thinks it is important to emphasize that what carries on is not a complete person, but only part of the person. The reason is that he thinks that the body is part of our nature, and something we cannot be complete without. Unlike Plato, he does not think of the body as a kind of prison of the soul, and he does not think of death as a kind of “liberation” of soul from body.

He thinks that a resurrection of the body – the restoration of the body to its soul – is necessary for a complete human person to exist again after death. And he thinks that God can and will make this happen. But he does not think that that part of the story can be proven through philosophical arguments. In his view, you have to turn to theology and divine revelation to know about that.

But he thinks that purely philosophical arguments, apart from any appeal to divine revelation, can at least show that the human soul is immortal in the sense I’ve been describing. And so he thinks that a purely philosophical analysis of human nature can show that a kind of dualism is true – that human beings are a composite of the physical and the non-physical, of perishable body and immortal soul.

Some implications

As Aquinas understands them, body and soul are not two substances, two entities that might exist entirely independently. There is only one substance, the human being as a whole. If a body is alive, then necessarily it must have a soul, since the soul just is the substantial form that gives the body the distinctive powers of a living thing. So there is no such thing as a living body without a soul. And though the human soul can continue to exist beyond the death of the body, it does not carry on as a complete substance in its own right, but rather as an incomplete one – as the human being reduced to just the intellect. We’ll see that this makes Aquinas’s brand of dualism very different from that of Descartes.

Because of this intimate connection between body and soul, Aquinas would not think that reincarnation as usually understood is possible, even in theory. The rational or human soul is the substantial form of the human body. Hence there is, for Aquinas, no such thing as a human soul being reincarnated in the body of (say) a dog or a fish or any other non-human animal. But there is also no such thing, in his view, as your soul entering into someone else’s body (as in movies like Freaky Friday). Your soul is the form of your body, so if it is informing some bit of matter, then that matter is going to constitute your body, specifically, not some other body.

Not possible, in Aquinas’s view

The cannibal problem

Not only that, but Aquinas thinks that the connection between a soul and its particular body is so close that, if God is to resurrect a human being by restoring the body to the soul, he would have to restore to it the specific bit of matter that had originally been associated with it. For example, if Fred dies and his body is buried in a certain coffin in a certain cemetery, then when God resurrects Fred, he unites to Fred’s soul that particular body in that particular coffin – rather than just any old bit of matter.

In most cases that is pretty straightforward. But Aquinas imagines a critic raising the following objection. Suppose Bob is a cannibal, and that after Fred dies, Bob eats Fred’s body. The matter that once made up Fred’s body now becomes incorporated into Bob’s body. Now suppose Bob himself died. Can God resurrect both Fred and Bob? It might seem not, if he has to use the very same matter that made up their bodies. For that matter once made up Fred’s body but then later made up Bob’s. So it might seem that God could resurrect Fred or Bob but not both. Commentators on Aquinas sometimes call this “the cannibal problem.”

Cannibal? No problem!

Aquinas doesn’t think the problem is that serious, though. He notes that the matter that makes up the body is constantly changing anyway, though it does so in a gradual way. The matter that makes up your body now is not exactly the same as the matter that made up your body a year ago. The shedding of skin cells, the eating of that year’s worth of food, etc. have all made a difference.

Hence, in the case of Fred and Bob, Aquinas thinks that what God would do is use some of the matter to resurrect Fred and some of it to resurrect Bob, and then make up the gap in each case by adding new matter to each of their bodies (just as new matter would have been added to each of them if they had stayed alive and eaten).

Whether or not the cannibal problem is easy to solve, though, it is worth noting because it underlines, once again, how intimate the connection is between your soul and your body, on Aquinas’s view. Though he is a dualist in the sense that he thinks there is more to you than matter – and indeed, a part that survives the death of the body – he wants to emphasize that the body is our natural home, as it were. So much so that you are not really complete without it. Like Aristotle, he defines us as rational animals, and both parts – the immaterial rational part and the material animal part – are essential.

As we’ll see, in modern philosophy, Descartes on the one hand and materialists on the other move away from this conception of human nature. The real you, for Descartes, is the immaterial rational part, which he understands to be a complete substance in its own right, to which the body is not essential. By contrast, for the materialist, the real you is the body, and there is no immaterial aspect to human nature at all.

Here are some optional YouTube videos on Aquinas’s view:

Aquinas 101 on the Immortality of the Soul:

https://www.youtube.com/watch?v=NTSQPDOn0xc

iAquinas on Is the Soul Immortal?:

https://www.youtube.com/watch?v=NHMkPtA9v40

iAquinas on The Soul Separated from the Body by Death:

https://www.youtube.com/watch?v=WnA7nmKzho4