Summa Theologiae I q. 88

I find Summa I q. 88 extremely disappointing, though disappointments are proportionate to expectations, and it’s altogether possible that I have unreasonable expectations.

Q. 88 concerns the knowledge we can have in this life of things above the physical world, and since Aquinas defines metaphysics as such a knowledge, the existence of metaphysics is here at stake. For those of us who are trying to be both metaphysicians and Thomists, this article should be a one of our central guiding lights. And yet, to be blunt, Aquinas never gives a satisfying answer to how we might know anything beyond the physical world, and he avoids pure agnosticism by ad hoc qualifications and unexplained denials that leave obvious questions unanswered. His response to a. 1 objection 5 is a good place to start. The objection reads:

As sense is to the sensible, so is intellect to the intelligible. But our sight can see all things corporeal, whether superior and incorruptible; or lower and corruptible. Therefore our intellect can understand all intelligible substances, even the superior and immaterial.

Aquinas responds:

Sense knows bodies, whether superior or inferior, in the same way, that is, by the sensible acting on the organ. But we do not understand material and immaterial substances in the same way. The former we understand by a process of abstraction, which is impossible in the case of the latter, for there are no phantasms of what is immaterial.

So “we do not understand material and immaterial substances in the same way”. So then, how do we understand them? This is the whole point of q. 88, and yet at the crucial moment all the reader hears is crickets.

What is even more striking, St. Thomas follows up this question with a denial that we can come to know immaterial substances from material things. At the very least, this indicates that STA thinks that the denial is closer to the truth. Every argument that we can reason from the things of the world to metaphysical reality is here an objection, but the responses to the objections leave one bewildered. After raising the objection that there is actually a science of metaphysics, the response is:

Science treats of higher things principally by way of negation. Thus Aristotle (De Coel. i, 3) explains the heavenly bodies by denying to them inferior corporeal properties. Hence it follows that much less can immaterial substances be known by us in such a way as to make us know their quiddity; but we may have a scientific knowledge of them by way of negation and by their relation to material things.

“Principally” is an obvious wiggle word. Thomas knows he can’t claim that our knowledge of metaphysics is purely negative, but this means that we must have positive knowledge in some way. This seems to be the point of adding the last four words of the response. Still, “relation to material” is not necessarily opposed to “negation”, since negation itself is a sort of relation. So there seems to be something wrong with saying the science is “purely negative” (it’s hard to see how this would be different from agosticism) but STA doesn’t seem to want to admit any positive grasp of the object either. Merely mentioning “the way of causality” or “the way of excellence” doesn’t seem to remedy the problem here, since if all one can say about, say, a causal relation is exhausted by our setting it apart from material existence, then the whole causal relation is known by negation. But if something else is known, then what is it?

St. Thomas makes a great deal of the idea that the human intellect is not proportionate to immaterial things. This idea, however, is not developed, and as far as I can tell all it means is to relate to another in such a way as to know it. But then it explains nothing to say human minds can’t understand immaterial substances since they aren’t proportionate to them, since this only amounts to saying that we fail to know something because we fail to relate to it in a way that is adequate to know it; which says nothign more than we fail to know it because we fail to do so.


  1. JT said,

    September 13, 2011 at 1:59 pm

    “The former we understand by a process of abstraction, which is impossible in the case of the latter, for there are no phantasms of what is immaterial.”

    I’m curious. What would be a satisfying answer for you to the question of how we understand immaterial substances? Even a negative differentiation from material knowledge seems enough to show the necessity of positing immaterial knowledge, and if he describes the process, as in this quote, is that not quite enough? I’m just not sure how he could have gone further.

  2. September 13, 2011 at 3:43 pm

    There is no description of a process other than abstraction in that quotation.

    A satisfying answer would require saying how we can have a positive knowledge of the immaterial at least secundum quid.

    To anticipate one possible answer, it won’t solve anything for a Thomist to invoke the idea of “separation”. What is being separated? Material reality and existence? But if all knowledge is abstractive, then “being” or “existence” is nothing other than the vaguest grasp of what is, in fact, a material thing, and so the putative act of “separation” would be contradictory – nothing other than the claim that a material thing is not a material thing. Separation presupposes another mode of knowing. St. Thomas clearly hints at it. What is it? It’s not that I think that the notion of separation is bogus, but that St. Thomas sees it as based on some other process that he only hints at.

    My sense is that STA has to develop the idea that there is simply something divine in man, and that it is only so far as there is something in him more than human that he can do metaphysics (he does say that metaphysics is “borrowed” from God, and that man can only do it in the measure that he is a pure spirit). I also think he needs to develop the opposition between ens commune/ens as the most potential and ens as the most formal concept. He clearly thinks that one can go from a grasp of a transcendental concept to seeing the reality of God (this is the structure of the fourth way) but the details of how this is possible are never laid out.

  3. September 13, 2011 at 8:56 pm

    Recall that the Summa Presupposes a vast curriculum in Philosophy and so Aquinas skips many steps in his arguments and presumes that the reader can fill in the gaps. In this instance I would suggest that Aquinas is using immaterial in a strict sense. Remember, for Aquinas, the rational soul is not completely immaterial. Heck, the sensible soul is a material soul. Perhaps the key here is clearly understanding what Aquinas means when he uses the term ‘immaterial’.

    • September 14, 2011 at 8:03 am

      There were times in my life (and they might come again) when a response like “he solves this somewhere” or “he speaks in a strict sense here, not a broad one” or “do not demand more clarity than the subject allows” would have been a satisfying response. For all I know, if someone would have written exactly the post I wrote here and I read it on another blog, I would have given all these answers myself. Perhaps these answers are reflections of the only correct outlook one can have, though I’m at a point now where I doubt that. I am bothered by the distinct impression that STA is avoiding difficult conclusions by hiding behind wiggle words and vague qualifications, which, if one draws out what they must mean, would have far reaching consequences. At some point, the vague qualifications need exposition. We can’t just keep saying “we only know by abstraction” or “our soul is a material form” in one context and then resort to vague hints about “some other way” or “not completely immersed in matter” at the crucial moment when abstraction appears not to explain what we are claiming to know, or when we see the need for the soul to know something higher (to say nothing of what “immersion in matter” means).

      • September 17, 2011 at 3:12 pm

        I agree completely. My point is simply that Aquinas doesn’t solve these ambiguities elsewhere. Rather, he presupposes a body of knowledge from the reader that we no longer possess. A clear example of this is the differences between the 5 ways in the ST and their equivalents in the SCG. As a result I’ve begun a personal study to try and overcome this lecunia. I think that to fully realize the Thomistic renewal called for by Leo XIII we need to go back to a rigorous study of such material and then reread Aquinas in light of the material that was actively influencing him, e. g., Medieval developments of the philosophy of Aristotle on all fronts.

  4. September 13, 2011 at 11:30 pm

    Through a glass, darkly. Isn’t analogy a missing link here, and isn’t the context you describe above the reason for its massive importance in the entirety of St. Thomas’ thought?

    • September 14, 2011 at 8:26 am

      My question here is whether abstraction allows for negations, causal chains, or analogies to terminate in something supernatural. On my understanding of Scotus, he says that this is only possible if “being” has some one undifferentiated meaning for all that exists. Cajetan responds by positing something called “participative” knowing, but he only allows this as a dialectical option, and it is not clear what he means. At any rate, St. Thomas seems to refute the consequence “if some material thing is a participation, then he who knows material things can know them as participations” in his response to q. 88 a. 3 ad 3, though one might find someway to wiggle out of this by his saying that the participation is not perfect (and yes, I know that STA is refuting the idea that God is known first, but in so doing he deals with a participation objection that has a wider application).

  5. RP said,

    September 14, 2011 at 4:29 am

    Short answer: intuition.

    Longer answer (my usual nonsense):

    That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon and our hands have handled, of the word of life.

    For the life was manifested: and we have seen and do bear witness and declare unto you the life eternal, which was with the Father and hath appeared to us.

    That which we have seen and have heard, we declare unto you: that you also may have fellowship with us and our fellowship may be with the Father and with his Son Jesus Christ.

    Things are more than meets the eye. As Pieper says Guardini says, “things have the character of word”. I suppose this means things have meaning. Meaning means making sense. Making sense means understanding. Understanding is intuition (as in knowing first principles).

    Reason is the failure of intuition.

    Metaphysics is a back and forth between reason and intuition.

    Maritain: the intuition of being.

    • September 14, 2011 at 8:13 am

      If we intuit a reality above matter, a proof for it becomes superfluous. No one proves what he sees.

      If our intuition of being is of some reality that is undifferentiated between the material and metaphysical, then we are Scotists.

      And either way, if we posit an intuition to allow for the existence of metaphysics, how are we not begging the question of whether there is a science beyond natural science?

      • JT said,

        September 14, 2011 at 2:38 pm

        Doesn’t this intuition limit itself to the first principles of Being, though? Like we are able to use the principle of non-contradiction without reflexively knowing it?

        And couldn’t we avoid begging the question by proving the existence of the intuition on other grounds, a posteriori?

        These are really interesting questions you raise, though many of your answers go way over my head. I enjoy the blog!

      • September 14, 2011 at 3:16 pm

        Perhaps, unless you mean “being” as the Laval school takes it, as just the vaguest grasp of a material thing. But if you mean something else, what is it and how do we know it? I’ve tried to work out some idea of this, but you have to offend half the world of Thomists every time you do so.

      • RP said,

        September 15, 2011 at 2:46 am

        If we intuit a reality above matter, a proof for it becomes superfluous. No one proves what he sees.

        Can’t prove everything, even in mathematics.

        If our intuition of being is of some reality that is undifferentiated between the material and metaphysical, then we are Scotists.

        Thomists (of sorts). But acknowledging Scotus was right twice a day.

        And either way, if we posit an intuition to allow for the existence of metaphysics, how are we not begging the question of whether there is a science beyond natural science?

        Natural science shows the existence of immaterial things. But can’t investigate them under the rubric of motion. Ergo, etc as The Smithy is always saying (leaving me completely in the dark).

  6. September 14, 2011 at 2:16 pm

    I worry somewhat, given what you’ve said in the post and in the comments, that you aren’t making a sharp enough distinction between proving that something is and proving what it is, and that this is obscuring the issue throughout.

    • September 14, 2011 at 3:11 pm

      I might be muddling the difference between real being and being as the truth of propositions too. Still, I don’t know that either the post or the development it’s gone through in the comments is unified enough to involve one mistake. I’m complaining about all sorts of unconnected things.

      • September 14, 2011 at 5:09 pm

        I’m intrigued by the possibility that abstraction might be the abstraction of a quiddity, and so even if we consider abstraction according to its limitations, the knowledge that something is would not have to fall under those limitations. Abstraction could thus be a limit on what but not on that.

        But I don’t know how in the world I would start proving that, and I’d need to do a lot more work on what it meant to know how to flesh out the difference.

  7. Brandon said,

    September 14, 2011 at 8:04 pm

    JT’s mention of the principle of noncontradiction actually raises a very important issue; because, of course, on Aquinas’s view the principle of noncontradiction is the first indemonstrable principle following on the understanding of being (and non-being). (Very nice summary of this, of course, in ST 2-1.94.2.) So that naturally suggests, at the very least, that a closer look at how we know the principle of noncontradiction might result in some progress on this question.

    • September 17, 2011 at 3:17 pm

      Isn’t the problem the issue of giving an account of conatural knowledge?

  8. Jhf884 said,

    September 20, 2011 at 9:37 am

    You want Thomas to say one thing, but, it seems to me that he is saying something else. If I’m right about that, then Thomas isn’t using “wiggle” words, you are just trying to force a reading onto the text that the text cannot comfortably support. Namely, that we have per se knowledge of separated substances.

    The easier explanation is that Thomas does not believe that we have this knowledge. As we’ve debated before w/r/t Analogy, I think this is the right reading, and I don’t think analogy gives _us_ that knowledge, though it does allow us to say _that_ God must be such-and-such (e.g., good, just, one, etc.), _we_ don’t know this directly or per-se. That’s why Thomas consistently affirms the via negativa. Analogy gets around part of the problem, but we still only have knowledge according to our naming, not according to the thing-existing-in-itself (i.e. I know what I mean by calling God “good”, I do not know what God-who-is-goodness-itself actually *is*).

    This post touches on something that always bothered me at TAC–namely a lot of people there seem to want to affirm our knowledge of God to the point of annihilating any real sense of the via negativa. I thought then, and am more certain now (though I am far from a master Thomsist!), that this was a deep misreading of Thomas.

    “You want it to be one way, but it’s the other.” –Marlo, The Wire.

    • September 20, 2011 at 12:02 pm

      St. Thomas (following Met. Bk. VI) defined metaphysics as the knowledge of what exists without matter or motion. The onus is on him to come up with some plausible account of how we know these things, and this is clearly (one of) the main problems that is being addressed in this question. So far, I think Brandon’s account is the most promising: make a sharp division between the knowledge that something is and the knowledge of what something is. There will be problems here too, but it would be worth looking into the account.

      I’ve said the same thing from the beginning: our knowledge of the metaphysical cannot be purely negative, for the simple reason that pure negation is agnosticism, not apophatism. The difficulty is account for what we will say about this positive knowledge. We can qualify this positive knowledge with as many scholastic adverbs, distinctions and prepositions as we want (for example, I have no immediate reason to object to you insisting that the positive knowledge cannot be a “per se” knowledge, etc.), but at the end of the day we have to have something that counts as bona fide positive knowledge, and it is not obviously fruitful or unproblematic to try to derive this positive knowledge out of a doctrine of abstraction. It is not clear to me whether Augustine’s epistemology would be better suited as a foundation for metaphysics.

      • September 20, 2011 at 12:42 pm

        I was reading some things today, and suddenly I realized that Aquinas may well have had the same trouble with Aristotle that you are having with him. Aquinas explicitly says in several places (cf. De Anima around about n. 736) that he is missing part of Aristotle’s Metaphysics — he sees a gap in Aristotle’s discussion and thus assumes that it has either been lost or not yet translated. And what does Aquinas think lacking? An account of separate substance that handles several problems raised by Aristotle but never, apparently, solved by him, something going beyond Met. Lambda. So at least there’s an apparently analogous problem.

        (Re the Augustinian point, I have wondered, actually, if this is one reason for Aquinas’s embrace of participation — that when Aristotelianized a little bit by extrapolating what Aristotle would likely say, it makes headway to at least some extent on at least some of the problems he thinks must be dealt with in his posited missing Aristotle — e.g., how the intellect is related to separate substance. From St. Thomas’s view the Platonists are generally only approximate and often metaphorical, but they are also generally right as long as you take the approximation and metaphor into account, so he can use the Dionysian, Boethius, and Augustine to cover some gaps. I don’t know if this is true, but it’s an interesting thought.)

        The beginning of De substantiis separatis is pretty interesting in this regard; an immense amount of emphasis on the argument from motion, but also one of the points at which Aquinas starts with Aristotle but Platonizes him a bit.

      • September 20, 2011 at 7:16 pm

        While noodling around at JSTOR, I found this which might very well have been what you were reading, or else it would dovetail w/ it perfectly.

        Full citation, If there are problems:

        The Separate Substances and Aquinas’s Intellectus Agens

        Héctor Zagal Arreguín

        Revista Portuguesa de Filosofia, T. 64, Fasc. 1,

        Skip to p. 12

      • Jhf884 said,

        September 20, 2011 at 1:54 pm


        I think Brandon’s suggestion is exactly right–with Aquinas (in my reading) using Analogy to fill in the details (i.e. we know the _that_ to be like this rather than like that, though we still don’t know it directly). As you say “Abstraction could thus be a limit on what but not on that.”

        But I think you underestimate the power of apophatic knowledge. Once we know _that_ something exists (w/o knowing it directly) we can use the via negativa to eliminate certain possibilities. What’s left is indirect knowledge through (a) the proof of the existence of God, and the apophatic discussion of his attributes, and (b) our knowledge of the soul (which I must admit, has always been difficult for me to understand). This is why the Laval school stressed the primacy of the Physics against the “transcendental” Thomists and others. Our bona-fide direct knowledge is the knowledge quia sunt that we gain from our reasoning about material form

        Aquinas is almost as much a disciple of psuedo-Dionysius as he is of Aristotle. And for Thomas, there wasn’t really any contradiction between the two. In other words, you seem to be faulting him for “hedging on” our knowledge of separated substances. I think what Thomas is doing (consistently throughout his writings, as far as I am aware) is denying that we have any per-se or direct knowledge of separated substances. This isn’t a bug, but a key feature, which he gets from his reading of Aristotle (see commentary to Metaphysics II lect 1). In a sense, we *cannot* know metaphysics like we know physics (at least, on a natural level).

        So, I guess I don’t see any inconsistency or contradiction in what you’ve pointed out. If I understand what you are saying, it seems to me that you misunderstand “the whole point of” ST I Q 88.

      • September 20, 2011 at 6:39 pm

        We might be talking past each other here.

        Once we know _that_ something exists (w/o knowing it directly) we can use the via negativa to eliminate certain possibilities

        True, once we have a bona fide metaphysical proof, we can certainly go on and polish up the proof with negations. Why would I object to that?

        I don’t know how I could be taken as arguing that our idea of the SS’s must be really “direct” or “per se”. I’ve said nothing but that I wanted some account of how one gets positive knowledge at all, not how one gets per se or direct knowledge. Apparently (taking the opposite of all your qualifications) you think that our positive knowledge of the immaterial is indirect and per aliud. (Feel free to add more qualifications.) Fine. So how does this positive knowledge, with all the qualifications you want to impose on it, happen? Is our positive idea of the immaterial an idea of “cause”? But the theory of abstraction (or separation, if you want to view it as different) only seems to supply us with a notion of “cause” that is a vague grasp of a physical cause. But how does a vague grasp of a physical cause tell you about a non physical one? Analogy will allow you to name the thing once you find it, but how do you find it? (N.B. If you think you have a grasp of “cause” that includes both the SS’s and physical things indistinctly, then you’re a Scotist; and if you posit such a concept b/c you claim the knowledge of God is possible you are begging the question).

        Again, I think I favor an odder response than anyone. Something along the lines of Aristotle’s claim that there is something divine in man which most is man. Once one gets a good look at the Agent Intellect, for example, it looks like a god. STA struggles to articulate how the soul could give rise to such a thing.

      • September 21, 2011 at 8:50 am


        Yes, that was exactly what it was; looking into various articles on the theory of participation. I didn’t think the argument all that well argued, but the issue of separate substances / missing Aristotle / participation was set in motion.

      • JeffC said,

        September 22, 2011 at 11:13 am

        Does not the proof of the existence of God at the conclusion of the prima via at SCG Bk. 1, Ch. 13 (and again at the end of In VIII Physicorum) suffice for the proof of a being that is outside of matter and motion? If so, would that not provide an entry into the study of metaphysics?

        I don’t have the text available to me at this writing, but Aquinas (in In VIII Phys.) states fairly clearly that the First Mover (God) is outside of matter and motion and that he does not reach this conclusion by a via negativa. Once one attains knowledge of the existence of things outside of matter and motion, then one can begin metaphysics.

      • September 22, 2011 at 11:37 am

        The question here and in q. 88 is epistemological. What is the structure of the mind that allows for metaphysics? Even if we take the proof as a given, what account must we give of the mind? Is there a non-question begging way of articulating the structure of the mind that allows for metaphysics?

      • JeffC said,

        September 29, 2011 at 3:07 pm

        I do not know that this answers the question, but it does point in the right direction. St. Thomas writes at IN XII METAPHYS., Bk. 4, L. 6, para. 605:

        “…it must be noted that, since the intellect has two operations, one by which it know quiddities, which is called the understanding of indivisibles, and another by which it combines and separates, there is something first in both operations. In the first operation the first thing that the intellect conceives is being, and in this operation nothing else can be conceived unless being is understood. And because this principle–it is impossible for a thing both to be and not be at the same time–depends on the understanding of being (just as the principle depends on the understanding of the whole and part), then this principle is by nature also the first in the second operation of the intellect, i.e., in the act of combining and separating. And no one can understand anything by this intellectual operation unless this principle is understood on by understanding being, in a similar way the principle that every whole is greater than one of its parts is understood only if the firmest principle is understood.”

  9. Peter said,

    September 20, 2011 at 1:22 pm

    In his commentary on the Metaphysics II lect 1, he says: “And since this process of knowing truth befits the nature of the human soul insofar as it is the form of this kind of body (and whatever is natural always remains so), it is possible for the human soul, which is united to this kind of body, to know the truth about things only insofar as it can be elevated to the level of the things which it understands by abstracting from phantasms. However, by this process it cannot be elevated to the level of knowing the quiddities of immaterial substances because these are not on the same level as sensible substances. Therefore it is impossible for the human soul, which is united to this kind of body, to apprehend separate substances by knowing their quiddities.”

    This fits with what Brandon is saying. Also, in Q.D. De Anima 16, he reiterates the distinction:

    “Consequently, in opposition to this doctrine, we must maintain that the intellectual soul of man, by being united to the body, has its vision turned toward phantasms, and is informed in its intellection only through species acquired from phantasms…. Hence the soul, while united to the body, is capable of attaining a knowledge of separate substances only so far as it can be led thereto through species derived from phantasms. But in this way the soul will not attain quidditative knowledge of those substances, because their order of intelligibility transcends completely that of the intelligible species of material things abstracted from phantasms. However, we can in this way attain some [non-quidditative] knowledge of those separate substances, we can know that they exist (quia sunt); just as from lowly and deficient effects we proceed to lofty causes, but only to the extent that we know they exist. And while we know that these superior causes exist, at the same time we know that they are not of the same nature as their effects, and this knowledge consists in knowing what they are not, rather than what they are. Consequently it is true to say that, inasmuch as we grasp the quiddities which we abstract from material things, our intellect can, by turning to those quiddities, apprehend separate substances, so that it knows them to be immaterial, just as are the quiddities themselves which are abstracted from matter. Thus, thanks to the reflective power of our intellect, we are brought to a knowledge of intelligible separate substances….”

    St. Albert’s take (found in his commentary on the De Anima, book III, where the question of how we know immaterial things is taken up) is waaaaay different from what I expected. It might be worth checking out, if only to compare the two, especially if you are thinking of looking to St. Augustine.

    Also, you might find something fruitful in (re)reading the CDK dissertation on the Role of Negation (esp. the chapter on our knowledge of God). Your position on negative knowledge seems less nuanced than it will need to be to answer this question.

    My two cents….

  10. RP said,

    September 21, 2011 at 4:11 am

    Not too many people have seen separate substances, but nobody has seen an Agent Intellect.

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