In our discussion of the earlier post, Kleiner recommended that I check out Aquinas’s argument against the corporeality of the intellect. There is a batch of arguments in Summa, book 1, question 75. I took a look at one, and worked through it, with the following results. I thought I’d broadcast them for general edification:
1. It is clear that by means of the intellect man can have knowledge of all corporeal things.
CH: Is this obvious, that there is nothing in the material universe we cannot understand? No, not obvious, though it might be true.
2. Whatever knows certain things cannot have any of them in its own nature; because that which is in it naturally would impede the knowledge of anything else. Thus we observe that a sick man’s tongue being vitiated by a feverish and bitter humor, is insensible to anything sweet, and everything seems bitter to it.
CH: So — if X has Y in its nature, then X cannot know Y? I can’t see why this should be true. Try out some parallel claims:
• “If X is the same color as Y, then X cannot contain Y” (false)
• “If X’s definition makes appeal to Y, then X cannot be used to define Y” (false — check out “between” and “interval”)
• “If X is related by blood to Y, then X cannot digest Y” (false, and sickeningly so)
It’s hard to come up with claims that are parallel in the right way, so these may not be relevant. So let’s address the claim directly. It seems to me that even if being material can skew one’s perceptions, and make knowledge harder, that would not prove that being material makes it impossible to know any other material thing. It may only make the task tricky.
3. Therefore (from #2), if the intellectual principle contained the nature of a body it would be unable to know all bodies.
CH: Well, that’s only as good as #2, and its consequent is absurd only if we presume #1.
4. Therefore it is impossible for the intellectual principle to be a body.
CH: Only as good as #3.
5. It is likewise impossible for it to understand by means of a bodily organ; since the determinate nature of that organ would impede knowledge of all bodies; as when a certain determinate color is not only in the pupil of the eye, but also in a glass vase, the liquid in the vase seems to be of that same color.
CH: Same objections as to #2. But also, it is not impossible to figure out what colors objects in a room really are even if you’re wearing tinted goggles. You have to compensate. Probably, Aquinas thinks such compensation is impossible for a material system. But that begs the question.
6. Therefore the intellectual principle which we call the mind or the intellect has an operation “per se” apart from the body. Now only that which subsists can have an operation “per se.” For nothing can operate but what is actual: for which reason we do not say that heat imparts heat, but that what is hot gives heat.
CH: Whatever. Okay with me.
7. We must conclude, therefore, that the human soul, which is called the intellect or the mind, is something incorporeal and subsistent.
CH: Not proven!