As far as I understand the Aristotelian arguments (including those made by Aquinas), they conclude from the determinacy of thoughts that intellectual thinking cannot be wholly material and so we have a soul, which is partially immaterial and incorruptible.

“Material” is just a word – it has to be filled with content. It does not seem so clear what Aristotle means with “material”, though it is obvious that it is much richer than the modern scientific conception of “material” (or rather “physical”). For example consciousness is clearly material for Aristotle.

If we look around us in the realms of physics and biology we presumably don't see anything as determinate (general, normative – thoughts are about the truth – and inherently meaningful) as our human thoughts (though, maybe, there are other intelligent species we don't know about). Some philosophers like Dennett (see his two-bitser example) would disagree, but we'll put those objections aside for now.

But imho from this we can at best conclude that humans are somehow special contrary to other animals (when – homo erectus? homo ergaster? – humans became special is another puzzling question, which probably can be turned into a counterargument, but let's leave that aside, too).

Of course we can use definitions for “material” and “immaterial” which are so, that humans have an immaterial component while other animals are wholly material. But what have we gained by this? The conclusion the Aristotelian or Scholastic wants to prove is some kind of incorruptibility of the soul.

Why should the immaterial not be corruptible, too?

It's a very defensible position to believe that our thinking can produce conclusions which are timeless: What Euclid proved is true forever and at all times. And his conclusions were about “objects” which are timeless and incorruptible, like geometrical figures, numbers or other mathematical structures (if they exist – what Plato would have accepted but Aristotle would afaik have denied).

But this does not help, either. A bit similar as Robert Pasnau argues in Aquinas and the Content Fallacy (thanks to the user Conifold, who mentioned it), I say: Like a teapot can contain tea, but it is not itself remotely tea-like, whatever makes it possible for us to have thoughts about what is incorruptible, it does not mean that it must be incorruptible itself.

Does all of what I wrote rest on a misunderstanding of the argument? Did some Aristotelian or Scholastic make the step from the determinacy of thoughts to incorruptibility more convincingly? Or can you give a good restatement of the argument which tackles those issues?

  • You may want to look at O’Callaghan's response to Pasnau and Ross's reconstruction of the argument. But this is not the only problem. Kant pointed out that these arguments can be flipped into "proving" that the soul is material, see What are the problems with the argument from immateriality of thoughts?
    – Conifold
    Commented Mar 1, 2017 at 3:53
  • @Conifold thanks, embarrassingly I don't have access to O'Callaghan's response. :-( I know it's not okay to ask you for a short summary, but if you find the time...
    – viuser
    Commented Mar 1, 2017 at 4:47
  • Unfortunately, I do not have the full text either, I only read the abstract at the link. I am not even sure Acta Philosophica posts electronic copies online, their website only has tables of contents and abstracts, so the full text may only be available in paper copy.
    – Conifold
    Commented Mar 1, 2017 at 21:33
  • @Conifold ok, the university library in my city has it in print. I'll have a look at it when I find the time.
    – viuser
    Commented Mar 2, 2017 at 0:02
  • @Conifold maybe Aquinas thought something like “If a universal ‘appears’ in a material object it can only do so by instantiation. Instantiation or de-instantiation is the hallmark of corruptibility. A circle in the imagination is an instantiation of a circle, so imagination is material. But in abstract cognition the universal can appear directly. So something incorruptible must partially be active, to prevent instantiation.” While this reduces the force of Pasnau's argument, I'm not so sure it refutes it. Or maybe this is misguided?
    – viuser
    Commented Mar 2, 2017 at 0:55

1 Answer 1


The reason is thus: immateriality has an unbound number of degrees of freedom in which to solve the massive constraint problem that is life itself, whereas materiality is bound to it`s matter and the history (some would argue design) of substantia.

To say "incorruptible", however, isn't quite right. It's just that, because of the unbounded nature mentioned above, it can rebound back to it`s purity quickly.

I would say animals are equally incorruptible, however.

As to why our thought should be unique to humans, the Bible remarkably has the most interesting answer: the apple. Sugar is the substance that creates the extra force in the brain that allows it its extra step of self-awareness. What was the first thing Adam and Eve did after eating it? A: Knew that they were naked.

Now presumably, it takes more than eating sugar for that self-awareness to occur otherwise other animals would exhibit these qualities This is where Jewish theology is a bit more sophisticated: it took also the act of disobediance. Going against the perfection of God by eating from the Tree which was explicitly forbidden was the act that some Jewish texts cite as the source of our freed-thought.

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