Saturday, 5 October 2013

Question 84 – The Soul’s Understanding of Corporeal Things


Questions Ia.q82 and Ia.q83 have provided a very short introduction to the will as intellectual appetite. Aquinas promises to return to give a comprehensive treatment of the will in the context of moral science in the second part of the summa. For the moment, he will return to the topic of the intellect to give a fuller treatment of some of the topics that he has already broached. In some ways this structure seems a little awkward, as if there had been a break in time between the composition of the questions before and after this point. Perhaps Aquinas had had his attention drawn to some more testing objections to his theses in the interim! At this point he gives a hierarchical overview of the next few questions: he will consider the intellectual knowledge of the soul united with the body in Ia.q84-88 and separated from the body in Ia.q89. In the consideration of the soul united with the body he will consider the intellectual knowledge of corporeal things (Ia.q84-6), of the intellect itself (Ia.q87) and of immaterial substances (Ia.q88).

Why this Question Matters

In starting his enquiry into the soul’s intellectual knowledge of corporeal things, Aquinas wishes, in this question, to understand the means by which it has cognition of them. He will come back to questions of the manner by which these means provide intellectual cognition and precisely what it is that we have cognition of in material things in the next two questions.

We’re already aware of the fundamental parts of Aquinas’s Aristotelian understanding of the act of cognition: The external material object affects the external sensory organs which provide data for the internal sensory powers to construct a phantasm (that is, a sort of representation) of the external object. The active power of the intellect, through the power of illumination, abstracts intelligible species from the phantasm and these latter are impressed upon the passive intellect. In this question Aquinas returns to first principles apparently in order to provide a systematic refutation of positions counter to that of Aristotle. Aquinas sees Aristotle’s position as a mean between two extremes. On the one hand we have an extreme form of naturalism that claims that the external object of cognition directly affects the intellect in a way parallel to the way that it affects the sense organs. On the other hand we have a Platonism that sees the intelligible as being separated from the object itself; both the actual object and our intellect participate in the separated form of the thing, so that our intellectual cognition of the object is indirect.

The Thread of the Argument

A1: The first stage of Aquinas’s deeper drilling down into the acts of the soul concerns the question of whether we have cognition of corporeal things through the intellect. After all, the intellect is the part of the soul which has knowledge of universals rather than of particulars. Therefore, since corporeal bodies have a fleeting and contingent existence, it seems wrong to assign our knowledge of them to the intellect.

Aquinas takes a quick trip through the history of the ancient philosophy of corporeal cognition, as reported by Aristotle. The earliest philosophers thought that the world consisted only of corporeal things; as these are in constant flux, our knowledge of them is correspondingly uncertain. As Heraclitus is reported to have said, “it is impossible to touch the water of a flowing river twice”; we don’t really know the river, as it is in constant change. Plato’s later approach to the question posited the separate existence of the ideas of things; these latter being what we know through the intellect. The unfortunate side effect of this theory is that we would then have no intellective understanding of particular corporeal bodies at all. Aquinas identifies the underlying problem with Plato’s approach as the belief that cognition of corporeal things involves the existence of the form of such a thing in the soul in the same way as it exists in reality. As the form of a corporeal thing must exist in the mind as a universal, Plato’s theory implies that it must exist in the same universal way in reality.

Aquinas is, of course, going to argue for Aristotle’s view: the form of a corporeal thing is received in the intellect in a different mode of being than it exists in reality. He argues that we already see these separate modes of being in the way that whiteness can be instantiated in different ways in different bodies and also in the way that sensation receives sensible forms. Therefore the soul does have cognition of material things through the intellect, but that cognition is immaterial, universal and necessary. What is received exists in the receiver according to the mode of the receiver.

Although corporeal things do have a fleeting and changing existence, this does not rule our having unchanging knowledge of them. Our very identification of a particular thing as a particular thing presupposes that we have identified elements of the thing that remain the same throughout change. It is of these elements that we have knowledge.

A2: Given that we do have knowledge of corporeal things through our intellects, do we have that understanding through the essence of the intellect? We recall Aristotle’s famous dictum from the de Anima that “the soul is in some sense all things”; our ability to have cognition of anything corporeal, and the fact that to have that cognition the forms of these things have some mode of existence within our souls together imply that our souls in some sense become what they cognize.

Aquinas again turns to the history of the philosophy of mind, recalling the materialist and Platonic alternatives whereby the forms of corporeal things exist in their natural mode of being in the mind; either as material forms according to the materialists or as universals according to the Platonists. Aquinas points out a number of serious difficulties for the idea that material forms exist materially in the intellect, concluding that they must exist immaterially in the intellect. The intellect abstracts species from not only from matter but also from the individuating material conditions in which a corporeal body exists; in this it is more perfect than the faculty of sensation which maintains the individuating material conditions. Having concluded that the forms of cognized corporeal bodies must exist in the soul in an immaterial way, Aquinas turns to the question of whether that existence is through the essence of the soul. The problem with this idea is that if an intellect has knowledge of corporeal things through its essence, it must have knowledge of all corporeal things through its essence; the essence, as essence, is what it is and doesn’t change through the accumulation of knowledge. However, it is only God that has such knowledge of all things; they pre-exist virtually in His intellect. Hence it cannot be true that human beings have knowledge of corporeal things though their essence.

A3: We saw in Ia.q55.a2 that angels know things through intelligible species that are connatural to them; they are created with a natural endowment of forms through which they know. Is the same true of human beings? The stage for this question is well set by the positions represented by the third objection and the sed contra. The former, following Plato’s Meno, argues that correct knowledge can be demonstrated by someone uneducated provided that they are asked appropriate questions in the right order; this demonstrates that they must know things prior to acquiring scientific knowledge of them and must therefore possess a natural endowment of intelligible species. The latter, on the other hand, is Aristotle’s famous dictum of the tabula rasa; we only come to have intellectual knowledge of things though our perception of things, before that we know nothing.

Aquinas comes down firmly in favour of Aristotle’s position. Prior to the perception of something through the senses, humans have cognition of it only in potentiality, both with respect to sensation and intellection. The senses are moved to actuality in sensing something and the intellect is moved to actuality by the process of abstraction from the sense image. The soul is not endowed with any natural intelligible species; at the start of its existence it is only in potentiality to acquire those species. Plato’s position, that the soul is created filled with species that we recall throughout our lives in the sensation and intellection of things, seems quite untenable. On the one hand it would require that we have these intelligible species within ourselves and yet have no knowledge of them prior to the apprehension of a corresponding external object (a sort of forgetting would seem to be required). On the other hand, it fails to explain the lack of knowledge someone born lacking a sense has of the corresponding sensation.

In answer to the third objection, Aquinas points out that a well ordered interrogation will actually provide an education in the topic at hand. One proceeds from commonly known first principles and knowledge, drawing out their consequences as new knowledge.

A4: If we consider sensation, we observe that sensible things existing outside the soul are the causes of the sensible species that exist in the soul. This might suggest that there should be an analogy with the intellect: surely there must be actually intelligible species existing outside the soul that cause the intelligible species in the soul? These actually intelligible external things must be forms that exist without matter (as matter individuates the thing, obscuring its universality) and therefore must be separated forms. So it would seem that the intelligible species that arrive in our intellects must either arrive from separated intelligible forms of the things themselves or must arrive from some external separated form that has already abstracted intelligible forms from concrete particulars.

The first of these alternatives was the position of Plato who claimed the existence of separated forms participated in by the concrete particular and by the intellect simultaneously in perception. The second position is identified with Avicenna, who denied that intelligible species exist per se but who insisted that they pre-exist in some separated intellects which form a hierarchy culminating in the agent intellect. From this separated active intellect, the intelligible species flow into our intellects.

Aquinas rejects Plato’s position on the nature of forms for the same reasons that Aristotle puts forward: the forms of corporeal bodies only exist naturally in their instantiation in matter: form and matter can be separated as the principles of things; they can be abstracted from each other in the process of intellection, but they do not exist naturally as different substances. But a further problem with the idea that actually intelligible forms flow into the intellect, already abstracted as it were, is that this makes the union of the soul with the material body completely superfluous; we’re left with the old idea that a human being is a soul inhabiting a body. The body itself is a principle (as matter is in combination with form) of the actually existing human being. The body, through its organs of sense, plays as essential a role to intellection as the immaterial soul.

A5: The Christian synthesis between Plato and Aristotle identifies that all created things pre-exist in God’s intellect; so a reasonable question to ask in this series is whether our knowledge of material things is due to these eternal conceptions. One might expect Aquinas to deny that we have cognition of things through these eternal conceptions, given his emphasis on the role of sense perception in cognition. However, the way in which the objections are phrased alerts us to the fact that the answer is going to be more subtle that we may have expected.

Aquinas makes a distinction between meanings of what it is to have cognition of something in something. In the first place we might use this phrase in the sense of seeing something in a mirror. In this sense, human beings in the state of their present lives do not have cognition of things in the divine conceptions; but the blessed in heaven do. The latter see God’s essence and in that essence see all things (Ia.q12.a8, but note the limits of that knowledge outlined in that article). Another sense in which may say that we have cognition of something in something is when the latter something is the principle of that cognition. As a simple analogy, we see things in the sun because the sun illuminates things for us to see. Aquinas claims, using scripture and the Christian tradition of divine illumination, that our participation in the divine conceptions is a means by which we come to know things. If we recall Ia.q79.a4, what Aquinas is saying here may become clearer: we perceive things through sensation and abstract intelligible species from the phantasms formed by the imagination. That abstraction is performed by the agent intellect which itself is moved by divine illumination; it is here that this participation in the divine conceptions occurs. So, we do not simply obtain our cognition of a thing through participation in the divine conceptions but in combination with the abstraction of intelligible species from the actual thing itself.

A6: Having eliminated a number of candidates and having elucidated others, Aquinas now turns to the role of sensation in cognition. The problem that early philosophers came to recognize is that sensation and intellectual cognition are of different orders. On the one hand, the earliest of naturalist philosophers collapsed these orders into one but later on Plato argued that they differ in order: the sensory powers are inextricably linked to the use of corporeal organs and the intellectual powers are unavoidably immaterial. Aquinas identifies that Plato took the consequences of this separation of orders of the sensory and the intellectual too far in his almost complete separation of their actions. For Plato, the role of the sensory powers is to nudge the intellectual powers into action; but the latter gain their cognition of things from participation in the eternal separated forms rather than from any aspect of the sensation of the thing.

Aristotle agreed with Plato that the interaction between the corporeal sensory order and the immaterial intellect posed a problem; if one holds that the agent must be more honourable than the patient in causality, then there will always be a problem with the material effecting cause in the immaterial. However, Aristotle insisted that the human being is a union of body and soul as matter and form and that one makes a mockery of the intimacy of this union if one separates the sensory and the intellectual to the extent that Plato does. The solution to this problem is the existence of the agent intellect; an active principle in the soul that is responsible for the abstraction of intelligible forms from phantasms for impression on the passive intellect. The phantasms constructed by the imagination from sensory input are not sufficient in themselves to impress intelligible species upon the passive intellect (as they are still associated with the material condition of the object of perception); they have to be made intelligible in actuality by the active intellect. Aquinas concludes by saying that although sensation cannot be considered to be the total and perfect cause of intellectual cognition, it is at least to be considered as the material cause of that cognition.

A7: Having abstracted intelligible species from the phantasms provided by the sensory powers, one might imagine that the intellect could just go off and do its own thing. Surely intellective understanding must be through these intelligible species alone? Aquinas argues that this position is mistaken; it completely underestimates the intimacy of the union between the bodily and the spiritual in humans. When we are in the act of intellection about something concrete we return to the phantasms from which the intelligible species were abstracted; when we consider something abstract, we think about it through phantasms associated with the abstraction.

The idea that the act of intellectual cognition involves a “turning to the phantasms” is Aristotle’s, recorded in book 3 of the de anima. Aquinas offers two arguments in support of this position. The first argument might strike one as being surprisingly modern: we observe that when people suffer injury to the organs associated with the power of imagination, their power to have actual intellective understanding of things is impeded even if earlier they had a thorough scientific knowledge of those things. If the power of intellection were simply associated with the intelligible species in the immaterial intellect, then this would not be so.

The second argument is based on introspection: when we attempt an intellective understanding of something we can see for ourselves that we do this by forming phantasms that illustrate what we’re trying to understand. Similarly, when we try to explain something to someone else we use examples from which they can form phantasms to aid their understanding.

Underlying these arguments is the principle that cognitive powers are proportioned to the things of which they have cognition. As an example, angels have a purely immaterial cognition of immaterial intelligible species implanted within them at their creation; they are not able to, nor do they have need of, turning to any phantasms abstracted from material cognition. In contrast, human cognition is of the quiddity or what-ness of material things existing in nature; the human intellect is intimately joined to its body and is thereby proportioned to the material. The quiddity of material objects is itself intimately united to particular material objects; therefore our cognition of them is though our external senses and our imaginations which form phantasms corresponding to the material objects. When we have intellectual understanding of material objects, we understand their universal aspects as instantiated in the particular; in order to inspect the universal nature of an object as existing in the particular, we have to turn to its corresponding phantasms in order to grasp the particular.

One might at this point ask how we can ever have an understanding of the higher, immaterial things in the universe. Aquinas answers that we ascend to an understanding of the immaterial by way of inference from the material; we have no direct perception of such things, we have to use our intellectual powers to infer the traces of the immaterial left in the material.

A8: The final article in this question provides a short coda on whether the intellect is impeded when the sensory power is inoperative. Aquinas’s answer that it is may seem puzzling at first from at least two points of view. Certainly, when I close my eyes my intellect certainly appears to carry on working as normal; and secondly, why is he asking this question? The answer to the first is that Aquinas is talking about the situation where the sensory power as a whole is inoperative; that is, all of the external and all of the internal sensory powers are not working! He gives the example of sleep as being a state in which this situation may occur. Aquinas’s argument is that in the situation that all of the sensory power is inoperative, we simply cannot have cognition of sensible things: neither right at the moment through direct perception nor through the imagination creating phantasms of things remembered.

When we consider sleep, we have to realize that the sensory powers can be more or less impeded in their operation depending on the state and quality of the sleep. Correspondingly the intellect will work under such circumstances to a greater or lesser extent. Aquinas finishes the question with the observation that those who reason in their sleep will find out when they wake up that the reasoning is faulty in some matter; such a great shame!

Having discounted sleep as a situation in which the sensory power is completely inoperative, Aquinas doesn’t then mention where we might find such a state. In fact, he will revisit this situation in Ia.q89 where he considers the cognition of a separated soul; it is in this state, where the soul is completely separated from its matter, that there is no sensory power. The consideration of the intellectual knowledge of a post-mortem soul is founded on the observations made in this article.

Handy Concepts

  • Aquinas’s commentary on Aristotle’s de anima is an intellectual tour de force that should be read by anyone interested in the latter. For our purposes, the commentary on Book 3 especially provides valuable background to this and the next few questions.
  • The form of a corporeal thing is received in the intellect in a different mode of being than it exists in reality. Our cognition of material things is immaterial, universal and necessary.
  • The soul is in some sense all things (Aristotle, de anima 3).
  • God has knowledge of all things through His essence; but we don’t, we have to work at it.
  • We’re not even up to the standard of the intellect of the angels: they have intellectual knowledge of things through intelligible species implanted at their creation. We have to slog along abstracting these intelligible species from the things that we come across.
  • Understanding the sensory perception and intellectual cognition of human beings involves understanding the consequences of the intimate relationship between body and soul. Failure to understand the latter will lead either to idealism or to an exaggerated materialism.
  • In abstracting intelligible species from phantasms, the agent intellect is moved by divine illumination. In this sense we may say that our knowledge of creation participates in the divine idea of creation.
  • Our intellectual cognition of material things is not simply through the intelligible species abstracted from those things. We always return to the phantasms of those things in order to put the universal aspects of the object of perception into its material context.
  • The intellectual power cannot function properly in the absence of the sensory powers.


  • In the third article Aquinas mentions Aristotle’s famous remark about the intellect being a tabula rasa, a blank slate. It’s important to realize that Aristotle is not claiming that we have no mental content prior to the perception of material objects, merely that we have no intellectual content. A misunderstanding of this point often occurs due to a failure to realize what Aristotle allots to the sentient powers as opposed to the intellectual powers. For example, he clearly recognizes what we would call animal instinct as existing in the estimative power.