Note on sensation

Aristotle said that one cannot err about the proper sensibles. It is not exactly clear what he meant, but St. Thomas took him to mean that one cannot err about the sensible so far as it is sensed. If I walk into a room and see a blue sheet of paper on the table, then I’ve seen blue and that’s all there is to it. Even if there was a blacklight in the room and the paper was in fact as white as snow, it remains that blue was in my consciousness. End of story.

I’ve always found something spooky or radical about the explanation since as a result of it the proper sensible itself becomes not just the object but also the contributions of the organ to the experience. The sense object is a melange of a thing in the world and the subjective and personal dispositions of the one sensing. One is hard pressed to see a difference between this account of sensation and the Kantian account of knowledge. It was strange that St. Thomas would take this line of explanation since easier and less radical ones easily suggest themselves (he could have said that we are less likely to err about proper sensibles than about common sensibles like size or number, or that the error in the organ is only from its corruption and so can never be attributed to the organ as such.) Instead, he took the opportunity to deny perfect objectivity to sensation. In fact, a perfectly objective sense experience involves a contradiction, since it would require a sensible that was not constituted by some subjective element. The objectivity of sense can only be taken from one element in it, but that element is absolutely inseparable from the subjective element. We can say that there is a difference between the subjective and objective elements or aspects of sensation, but we cannot say, and it is impossible that we ever could say, what the difference between these two elements of a sensation is.


  1. thenyssan said,

    November 8, 2011 at 12:33 pm

    I’m so glad you brought this up. Sensation and its error was topical in one of my classes recently and I realized I didn’t know how St. Thomas handled it. I gave them St. Anselm instead, which I found to be a highly liberating answer: the exterior senses don’t err; the inner sense does (de veritate vi).

    In that light, I was not immediately put off by (your presentation of) STA’s radical claim that sense cannot err. But your follow-up makes it sound like he’s saying more than the Anselmian position. Are you synthesizing Thomas or is there a text you can point me to?

  2. George R. said,

    November 10, 2011 at 7:26 am

    James, you should change the name of this blog to “Just Idealism.”

    • November 10, 2011 at 8:31 am

      Oh Bosh. This is the contrary opinion of Idealism and of Realism too. Idealism and Realism about sensation reduce to the same basic mistake: they claim an absolute distinction between the sense object and the contributions of the sense organ. The realists take this to mean we have some absolute grasp of some perfectly objective object, the Idealists take it to mean that we have no grasp of any objective object. They will fight with each other forever since they are simply the two sides of the same mistake. St. Thomas makes the sense object a mix of both with a subjective and objective element. One vindication of his theory is contemporary physics. It is the science of sensibles, and cannot be perfectly done without taking the contributions of the observer to the object into account.

      It’s important to note that this post is about sensation. The objectivity of intellect is a very different thing, and it is a mode of knowing differs in genus. Note that I said St. Thomas’s teaching about sensation is very similar to Kant’s theory of knowledge. The difference suggests a line of exposition and critique.

      • George R. said,

        November 10, 2011 at 3:36 pm

        James, I didn’t mean to sound as snarky as I did, but I’ve noticed what I believe are some very idealistic elements in your recent posts. For example, you wrote something about Einstein a while back in which you suggested something to the effect that “motion refers essentially to the observer.” In another post you said that miracles are a function of the state of mind of those who experience them. In another you wrote, “Teleology starts off as an observation.” That certainly does not sound like realism; yet you claim that it’s not idealism. But if it’s neither realism or idealism, what would you call it?

      • November 10, 2011 at 8:43 pm

        Part of it is dialectics, or just trying out ideas and seeing how they work – though I don’t know that I would ever write something just for kicks.

        We postmoderns can’t find any consolation in systems of thought anymore. We can’t just go all in with Pragmatists or Idealists or Existentialists, etc. For those of us who are Thomists, this means we no longer fulfill ourselves by trying to find ways in which Scotus is wrong or ways in which Aristotelian natural science can vindicate itself against, say, atomism or inertia. The goal is more towards synthesis, which involves a good amount of experimentation, dead ends, tinkering, etc.

        I’ll have to finish this later. Wife made me a giant birthday meal and am having a hard time words together making fit stuff.

      • MikeFlynn said,

        November 12, 2011 at 8:37 pm

        Motion is relative because there is no absolute reference frame. Witelo wrote so in the Perspectiva and Oresme cited him in considering whether the earth rotated on its axis. He concluded that there was so way to resolve the issue from sense experience since to a person fixed on the earth, the heavens seem to move, while to a person fixed to the starry sphere, the earth would seem to move.

      • November 13, 2011 at 9:43 am

        Thomists in general weren’t sensitive enough to this lack of a reference frame. This needn’t do away with there being a true telos to the motion – consider the difference between how the Lion and the crocodile hunt the gazelle. Both “close the distance” between them and their prey, and so use motion in hunting, and from this angle there is some conscious making of an act of the potential with privation, though from a purely quantitative perspective it would make no difference if you treated the lion’s motion as the same thing as the crocodile’s.

        Again, I grew up thinking that when I used a straw I was pulling the liquid up. After reading Pascal, I was startled to figure out that I was only creating a condition under which the atmosphere can push the liquid down. The account of the order of forces thus completely changed, though nothing changed in the order of intention. I still somehow do the same action irrespective of whether the per se motor of the action is one thing or its contrary.

        One might develop this point (object?) by saying that, say in the case of the straw, the “action” that did not change was an immanent act in the soul, whereas the “action” that did change (that is, the physical account that was wrong to the physical account that was right) was a transitive physical action. There seems to be a sort of indifference between these two orders so far as the first can have a telos and order irrespective of how the order of physical causes goes. Trying to get the physical causes right can blind us to the other order of causality which is in fact indifferent to how the order of physical causes moves. Nature doesn’t care whether the sun is at the center of a system, or the earth, or Ptolomy’s eccentric center, just as I don’t care whether I’m pulling up liquid or something else is pushing it down. Nature has its own end in mind, and even utter indifference in the order of physical causes need not change this. Would it matter if the straw were governed by sheer chaos that made its action 50-50 probability between pull and push?

  3. Chas said,

    November 12, 2011 at 10:07 am

    “If I walk into a room and see a blue sheet of paper on the table, then I’ve seen blue and that’s all there is to it. Even if there was a blacklight in the room and the paper was in fact as white as snow, it remains that blue was in my consciousness. End of story.”

    I don’t think this is what Thomas (or Aristotle) meant. The proper sensible of sight is color, and so, while the organ can distort the actual color, as in color blindness, the colored object still acts upon the sense organ, reducing it from potency to act. So the color blind person doesn’t have blue in his imagination, but color, and the infallibility of the sense with respect to its proper sensible is preserved.

  4. November 12, 2011 at 10:46 am

    I thought about that option and thought it might be a more moderate way out, but it seemed to me that if this account were true, then Aristotle would say that the sense was just as infallible about common sensibles as about proper ones. After all, you see “size” just as the eyes see “color”, and so just as we are not deceived in thinking an object has some color so we wouldn’t be deceived by thinking it has some size. But Aristotle says we are deceived about size all the time, by which he means, say, that we look at the sun and think it is bigger than the stars in Orion’s belt.

    And at any rate, I don’t think that’s how the text reads. I’ll go dig it up – but I’m pretty sure that the infallibility of the proper sensibles is based on their ability to be verified internally while the verifiability of the common sensible is based on extrinsic conditions (proper distances from them or measurement… since they are all based on quantity, my sense is that verification is based on measurement in one way or another, whether relative or absolute.)

    • November 12, 2011 at 11:17 am

      Just read Sentencia De anima, lib. 2 l. 13, and it is inconclusive. STA does not give an example of error with the common sensibles, and his account of the innerancy of the proper appears to be only Unusquisque autem horum sensuum iudicat de propriis sensibilibus, et non decipitur in eis; sicut visus non decipitur quod sit talis color, neque auditus decipitur de sono. So “sight is not deceived that there be such a color”. But we are agreed on that. I’ll dig around some more for the text I was thinking about in the post, which makes the proper sensible interiorly verifiable.

      • thenyssan said,

        November 12, 2011 at 5:04 pm

        On my drive home today I was wondering what your more radical reading would do to color as an accident. How would we still talk about the accident of color falling to a particular substance?

  5. November 12, 2011 at 10:44 pm

    RIght, here too I think we’ve got to say that color is not perfectly objective, and partially relative to the observer. A bee looking at a sunflower sees two colors on the petals whereas I only see one; just as deer see bright orange overalls as being the same color as trees.

    • thenyssan said,

      November 13, 2011 at 7:25 am

      Is there a way to capture what the accident of color would be then? “There is something in this substance that makes me see green and makes someone else see gray?” That “makes” still puts it all on the objective side it seems. So try “There is something in this substance that I see as green and that someone else sees as gray.” But then it seems we might as well just abandon color as an accident. Or redefine accident I guess.

      • November 13, 2011 at 9:09 am

        The colors are still diverse actualities or modifications in the medium of light, and by extension the in the medium of radiation. We can give precise mathematical accounts of them, but these are dialectical definitions which, if taken as a substitute for the proper sensibles, will collapse into incoherence. I don’t think we can give a proper philosophical account of the differences between any of the colors in the visible spectrum (I think we might have a shot with white, black, and gray) and I think it’s crucial to recognize that we can’t.

        As an interesting side-note, we might raise the question if quantum paradoxes arise from the idea that common sensibles like quantity can be absolutely separated from their foundation in the proper sensibles. We think we can have a true “wave” or “particle” – or even any sensible quantity at all – in an area where the proper sensibles cannot exist. Or perhaps this is the problem: physics has assumed for too long that the quantity of the common sensibles is identical to the quantity of a mathematical account. It can do nothing else, but that doesn’t make it so.

      • November 13, 2011 at 6:09 pm

        This article tries to answer this question:

      • November 13, 2011 at 6:14 pm

        To summarize, in that article Chris Decaen argues that in order to account for the various objections to color realism, one must distinguish the nature of color into formal and material parts. The material part is a bodily surface disposed so as to produce the sensation of a particular color; the formal part is the color which is seen by a well-disposed observer.

        I think of that second part as analogous to Aristotle’s definition of the moral virtues. Moral virtue is a principle of acting according to a mean as the prudent man determines it; similarly, a thing’s color is the color it is seen to have by a well-disposed observer (i.e. one with a healthy organ + in good conditions).

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