I don't understand two things

According to Aquinas, the rational soul is immaterial therefore it is immortal. I am wondering how he concludes that the rational soul is immaterial and also how an immaterial thing could be immortal.

Insofar as knowledge must be immaterial, and the impressed intellect in which it rests is immaterial, it is not something that by nature decomposes. There are no material parts to decompose the way matter does. If it doesn’t by nature decompose, it persists.

The natural order (including material beings and intellects) does require God’s concurrent action in order to continue to exist, but that’s already understood. In the natural order matter is put together and can decompose apart. Not so for that which is immaterial.

A hundred thousand more words could be written on the topic for justification, but I’m out for now.


It must? If we define knowledge as the storage and retrieval of information then that takes place in the brain. And we know that if we remove parts of the brain or they are damaged then specific memories are lost. I’m sure you’re aware of Alzheimers - which physically damages neurons. And knowledge is consequently lost.

It is very difficult for me to understand his language. Do you mind to elaborate these two posts in plain English so I can understand?

Knowledge to me is a form that can be experienced by mind. I cannot make a distinction between knowledge and material since matter to me is the stuff that we experience too.

How did you conclude that intellect is immaterial?


So, it is simple?

True. But you need to prove that it doesn’t decompose.

Apparently @Vico does not agree with you on the fact that the rational soul needs a sustainer.

I agree with Wesrock that rational souls (intellects) require God to sustain them. The soul is immortal and does not corrupt. An angel and a soul are incapable of decomposing.

But in another thread we agreed that the rational soul is simple therefore it doesn’t need a sustainer Please see post #68 in another thread.

In post #68 I answered your question “Does the rational soul need a sustainer?” with “So the yes answer was given before: …”

But something which is simple and incorruptible doesn’t need a sustainer.

The detailed answer was given earlier in this thread (Modern Catholic Dictionary).

  • Absolute immortality is possessed by God alone, who has no body and whose spirit is eternal by essence. He cannot not exist; he always has been and must be.
  • Natural immortality belongs to all spiritual beings, namely the angels and human souls, who are created indeed and therefore begin, but since they are simple by nature and have no parts, they will not die, although absolutely speaking, they could be annihilated by an act of God.

But this is just a definition/claim. I need to know how something which is incorruptible could possibly need a sustainer. Moreover, in this definition, it is mentioned that God can annihilate the rational soul which is not subject of our discussion.

There are two different words you are using that are not synonyms: incorruptible and immortal. So you need to know the meaning of subsistence. Subsistence is that perfection by which a nature is becomes itself and distinct from all other beings. Something subsists when it has being and operation through itself, not through union with another.

The human soul is incorruptible because it is impossible for a subsistent form to cease to exist. It is so, because that what belongs to a thing by virtue of itself is inseparable from it, and existence belongs to a form, which is an act, by virtue of itself. Accidents and material forms do not subsist, so acquire existence or loose it through the generation or corruption of composite things.

Aristotle also taught the immortality of the soul. I find it fascinating that the concept was/is not exclusive of Judaism/Christianity.

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Something which is incorruptible never perish therefore it is immortal.

Incorruptible means not subject to corruption or decay.
Immortal means something living forever.

The soul is immaterial and by nature incorruptible. This is because it is both subsistent and the souls operation is ultimately independent of the body. The body is material and by nature corruptible.

St. Thomas Aquinas wrote this in S.T. I, Q97: http://www.newadvent.org/summa/1097.htm

A1 Reply to Objection 4. The promised reward of the immortality of glory differs from the immortality which was bestowed on man in the state of innocence.

I answer that, A thing may be incorruptible in three ways.

First, on the part of matter—that is to say, either because it possesses no matter, like an angel; or because it possesses matter that is in potentiality to one form only, like the heavenly bodies. Such things as these are incorruptible by their very nature.

Secondly, a thing is incorruptible in its form, inasmuch as being by nature corruptible, yet it has an inherent disposition which preserves it wholly from corruption; and this is called incorruptibility of glory; because as Augustine says (Ep. ad Dioscor.): “God made man’s soul of such a powerful nature, that from its fulness of beatitude, there redounds to the body a fulness of health, with the vigor of incorruption.”

Thirdly, a thing may be incorruptible on the part of its efficient cause; in this sense man was incorruptible and immortal in the state of innocence. For, as Augustine says (QQ. Vet. et Nov. Test. qu. 19. Work of an anonymous author, among the supposititious works of St. Augustine): “God made man immortal as long as he did not sin; so that he might achieve for himself life or death.” For man’s body was indissoluble not by reason of any intrinsic vigor of immortality, but by reason of a supernatural force given by God to the soul, whereby it was enabled to preserve the body from all corruption so long as it remained itself subject to God. This entirely agrees with reason; for since the rational soul surpasses the capacity of corporeal matter, as above explained (I:76:1, it was most properly endowed at the beginning with the power of preserving the body in a manner surpassing the capacity of corporeal matter.

I don’t know his arguments but mine would.be this: a rational soul can think in abstract (be immaterial because material thoughts are never abstract) before it enters Judgement (is immortal, because souls live or die according to His Judgement) that is a rational soul is fully capable of thinking above immediate material needs, and draw spiritual conclusions, before it is sentenced to an eternal state.
This makes sense to me in the sense that a rational soul (human) is fully discerning in his or hers decisions.

If something doesn’t corrupt then it lives forever.

Although commonly used as synonyms, there is a formal distinction between the ideas of incorruptibility which refers to being or existence and immortality which refers to life or vital activity.

If the human soul is incorruptible then its existence cannot be destroyed with the corruption of the composite body. If the human soul is immortal then the life of the soul is not destroyed with the corruption of the body. Now, the human soul is not immortal because it is the cause of life as the same could be said of the souls of plants and animals which are not held to be immortal. So Aquinas just accepts on faith (not reason) that the soul is immortal.

Doesn’t something which corrupt lives forever (immortal)?

Something that is incorruptible can be made to not exist only by God, for God is the sustainer of it.

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