In the Summa Theologica, Question 108(5), St Thomas Aquinas writes:

Therefore, if anything is to be called by a name designating its property, it ought not to be named from what it participates imperfectly, nor from that which it possesses in excess, but from that which is adequate thereto; as, for instance, when we wish properly to name a man, we should call him a "rational substance," but not an "intellectual substance," which latter is the proper name of an angel; because simple intelligence belongs to an angel as a property, and to man by participation; nor do we call him a "sensible substance," which is the proper name of a brute; because sense is less than the property of a man, and belongs to man in a more excellent way than to other animals.

So intelligence belongs to man by participation. But does intelligence or rationality belong to other animals by participation?

I read this report, which suggested that apes also have a certain degree of intelligence and rationality:

According to scientists, “ape intelligence might be a bundling of skills related to learning, tool usage, understanding of quantities, and an ability to reach conclusions based on evidence and reasoning.”

According to Catholic theology in the tradition of St Aquinas, does intelligence or rationality also belong, in complete or partial form, to animals like apes? Or would they not have any "genuine" intelligence and rationality?

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    I'm not Catholic so I can't really answer your question but I can tell you according to science apes while possessing the ability to communicate in basic forms are not considered sentient based on the scale of reasoning.
    – user4060
    Commented Apr 4, 2013 at 15:03
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    The "report" also says that "A typical U.S. high school student barely has the skill to open a frozen burrito wrapper and punch “START” on a microwave oven." I am sure there must be better sources of animal facts out there.
    – Alypius
    Commented Apr 5, 2013 at 6:23
  • @Alypius Yeah, that "report" appears to be a lame attempt at comedy. ("A typical U.S. high school student cannot figure out how to pull his pants up around his waist.") Commented Apr 5, 2013 at 15:40
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    I know I may seem like I've got it out for you but I really don't. I think your question deserves consideration, but I still think this is as off-topic as the android question. I think your question is interesting but I still think it's an awful fit for this site. Because I think you deserve it, I took the time to clarify why I think it's a bad fit. You are free to disagree, but I wanted to take the time to explain my vote to close. It's covered in META at meta.christianity.stackexchange.com/questions/1639/… Commented Apr 6, 2013 at 3:22
  • Aside from the terrible "report", this is a perfectly reasonable question. The fact that the author actually dug up the relevant theologian shows research effort, and keeps the question focused on St Aquinas. There is no room for "discussion": the question makes it clear that answers must explain the views of St Aquinas (and closely related theologians).
    – Alypius
    Commented Apr 6, 2013 at 18:09

1 Answer 1


Now we define "intelligence" and "rationality" otherwise than Aquinas and other scholastic philosophers did. In Aquinas' teaching, reason or rationality is what we usually mean by intelligence - it's the ability to induce new knowledge by reasoning based on experience we get through senses.

"Intelligence" was slightly trickier. According to Aquinas and his contemporaries, angels don't need reasoning, they just "look and see" (this is metaphorical - they are immaterial, they have no eyes to see), they simply get the knowledge. Angels have some kind of telepathy - they give or get thoughts directly, they don't need to translate it to words, images or other symbols, share the symbols, and than translate them back to thoughts. We are material and our mind is restricted by lack of telepathy and the necessity to induce our knowledge from such symbols, from communication receivable by our senses.

Still, we participate on the simple intelligence of angels somehow. We can simply know something without any previous experience, or at least it was believed in Aquinas' times we can. Examples of this kind of knowledge mostly fail to the spiritual, to God's revelation and to mysticism. Anyway, it's distinct from either normal reasoning, or from instinctive "knowledge" which is animals' ordinary way of thinking.

Another aspect of the participation on the angelic intelligence is our ability to reason knowledge which cannot be derived from material world. Aquinas says that we can derive knowledge of God's existence from our experience with material world, but our knowledge of God's triunity and other fundamental theological aspects can be derived only from God's revelation, so this knowledge is proper to intelligence even though we learned it through reasoning. We can't learn this way anything angels can know, just some basic, easy-to-learn concepts.

Animals normally know things from their senses and instinct, they have no proper reasoning. But similarly as we can participate on angels' intelligence, they can participate on our reason somehow (not on angelic intelligence - it's too abstract for them). Thus they can be "intelligent" in the modern, broad meaning of this word, not in its medieval meaning. Using tools and reaching easy conclusions based on evidence learned through senses is an example of this participation on reason; still, apes can't really understand higher mathematics (AFAIK), so they don't possess our reason fully.

Tell me if you want more evidence; I derived this post mostly from Questiones disputatae 15 and from prologue and comments to its Czech edition.

  • Isidore of Seville wrote (Etymologiae 12) that some people thought apes (simiae) were so called because they imitate human reason (in eis similitudo rationis humanae). (The real reason, he says, is the Greek root simos, flat-nosed.) Hence also the modern English verb "ape", to imitate. This seems to fit the idea that their intelligence is a lesser, reflected version of our own.
    – James T
    Commented Apr 4, 2013 at 17:37
  • Thank you, your answer sounds nice to me, and the book is very enlightening.
    – Popopo
    Commented Apr 5, 2013 at 6:29
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    @Popopo: fine, then you can upvote and/or accept this answer :-)
    – Pavel
    Commented Apr 5, 2013 at 7:39
  • Okay, that's all right.
    – Popopo
    Commented Apr 5, 2013 at 8:27

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