This is part 4 of a series on the book The Logic of the Body by Matthew La Pine. For the others, see the top of Part 1.

In the previous post, we saw the need for an account of human psychology that can explain how emotions can be both a matter of moral responsibility and also bound up with bodily states that are not straightforwardly voluntary. Matthew La Pine’s argument is that the theological psychology worked out by Thomas Aquinas offers some assistance towards meeting this need.

Two health warnings regarding this post: firstly, this is my summary of La Pine’s explanation of Aquinas’ thought. So there’s a double gap between the below and Thomas himself. Although I’ve done my best to look up the references where the meaning was unclear and to understand the notions in light of what I know of Thomas’ thought, don’t treat this like an expert opinion. I’m just a reader with a little general background knowledge of medieval theology and metaphysics, trying to boil down Aquinas on the soul as The Logic of the Body lays it out.

Secondly, to modern minds Aquinas’ psychology gets a little weird. For example, one consequence of his view of the soul is that plants have souls (though not souls exactly like human souls). It’s also very detailed, with layers and powers and appetites (and those terms don’t always mean what they do in modern parlance). All I can say is, bear with it. If the resulting map can be demonstrated to better account for the phenomena of human psychology (which is La Pine’s claim), then even the weird bits might seem palatable in light of the explanatory power of the whole. Or at least, aspects of the model will commend themselves for further use, even if some modification might be necessary to the whole. ¹

Enter Aquinas

So what is so useful about Aquinas’ theological psychology?

Firstly, it is holistic: Thomas’ view is able to treat human beings as a thoroughly unified body-soul composite. This is due mainly to the way in which the soul is not identified with the higher powers of intellect and will and is therefore not synonymous with the mind. The soul is the “first principle of life”, the “form that vivifies and makes possible all human powers.” In metaphysical terminology, the body is the matter of which the soul is the form. Humans are not souls with bodies, we are embodied souls. The relation between the two is not instrumental, the soul using the body as a tool. The soul inheres throughout the body as suggested by the language of the breath of life in Gen 2:7: “The Lord God… breathed into his nostrils the breath of life and the man became a living being.” To lose one’s soul is not to lose rationality, but life. ²

So the relation between the soul and the body does not run in one direction only, “top-down”, with the soul (=mind) using the body, but is complex and bi-directional as the soul gives life and powers to all of the body, and bodily conditions “modulate” (La Pine’s term) the actions performed by the soul’s powers.

As a result, secondly, Aquinas’ psychology is tiered. Human powers (which operate holistically and are functions of the whole body-soul composite) are layered to encompass the complexity of human agency into rational, sentient and vegetative tiers, as follows:

Type of soul / powers	Division	Voluntary / involuntary	Possessed by	Works performed
rational	will intellect	voluntary	humans	intellective understanding
sentient	sense appetite [PASSIONS BE HERE] as movements of the sense appetite, involving bodily change sense cognition	partly voluntary	humans animals	sensory cognition movement
vegetative	natural appetite	involuntary	humans animals plants	nourishment

Hence that which is probably a surprise to modern ears, the discovery that Aquinas thinks that not only animals but plants have souls, as well as humans. This is perhaps made more understandable by recalling that Aquinas’ view of the soul is as the principle of life, not as synonymous with rationality. Plants and animals are living beings, and hence on his view have souls, but not souls of the same type as human souls. Humans possess rational souls, which encompass sentient and vegetative powers as well (three layer), animals have sentient souls which encompass vegetative powers (two layer), and plants have merely vegetative souls. The soul, as form, gives a living being its motive power.

Now all this kind of division may invoke shudders at the logic-chopping of the scholastics. But I would encourage those so triggered to suspend that judgement until they have seen the use to which La Pine eventually puts Aquinas’ model. We’ll also come on to arguments for the truth of something like this holistic view of the soul later.

Locating the passions

On Aquinas’ model, the emotions (passions) are a function of the middle sentient layer. The way this layer functions is crucial because this is where the complex interplay between mind and body is laid out. Sense cognition apprehends the objects of sense experience in two sub-rational ways: first-order recognition (this thing before me is a wolf) and second-order evaluation (a wolf is dangerous). Sense appetite then inclines towards or away from the representations that sense cognition places before it depending on the valuation (good or bad). This is not a conscious process – in fact, to jump ahead in La Pine’s argument, this is similar to a modern understanding of human subconscious judgements, which can recognise a dangerous wolf and prime the body for action before we are conscious of the situation.

But the fact that this process is sub-rational does not place it outside the influence of the rational faculties. There are two ways in which, on Aquinas’ view, intellect and will can exercise a kind of control over passions. Firstly, they can “modulate” (La Pine’s word) passions: humans can choose to stand in front of the dangerous wolf despite the priming and inclining of our sense appetite and inclination (moderns would perhaps say “instincts”). Secondly, the mental representations to which the passions respond can be shaped in advance by conscious thought; I can (to some degree) condition my instinctive response to a wolf by mental training. Or in La Pine’s other example, we not only may resist the urge to eat chocolate cake, we can alter our desire for it.

Herein lies the reason why passions are neither amoral, nor straightforwardly command-able: the lower faculties are independent sources of cognition and appetite that can function independently of and contrary to our conscious thoughts. This also accounts for the kind of inner conflict that we know can often characterise human psychological experience.

Herein lies the reason why passions are neither amoral, nor straightforwardly command-able: the lower faculties are independent sources of cognition and appetite that can function independently of and contrary to our conscious thoughts. This also accounts for the kind of inner conflict that we know can often characterise human psychological experience.

Aquinas is clear that the passions are moral. If they were simply disordered affections (as per the Stoics) then virtue would be an absence of passion, but if the passions are just all movements of the sense appetite, then “those moral virtues that have to do with the passions as their proper matter cannot exist without the passions” (p. 65). A virtuous person no longer desires to eat the whole chocolate cake, having so ordered their passions as to be moderate (rather than just having the willpower to resist the passion’s movement in this direction). This entirely consistent with our nature: “unlike God and angels, a human being’s good action exists with passions, just as it exists with the help of a body.” Passions are not a problem to be rid of, nor a non-moral component of existence, rather, “Because human beings are composite creatures with body and soul, knowing and enjoying the good is perfected by the overflow of joy into the senses; we must have our cake and eat it too.” (p.67)

Implications

Locating the passions in this way, as the middle semi-rational (=roughly, subconscious) layer of faculties of a unified soul-body composite, implies important things about human agency with respect to them. Positioning passions between rationality and involuntariness allows a range of scenarios of responsibility. In extreme scenarios like mental illness, the rational control of the higher faculties can be overwhelmed by the passions invoking disturbing apprehensions, diminishing or even removing the moral quality of subsequent acts. But the genius of this positioning is that the bodily context of passions is always in play, not only invoked in extreme cases. In a more everyday example, we can explain the way in which tears and sighs, a bodily response, are able to lessen sadness – and raise the possibility of managing passions by imagination (“Hope follows imagined victory”).

As La Pine puts it: “Emotions… are moral movements of the soul within composite corporeal organs modulated by corporeal qualities. The body seems to contribute a certain thickness or viscosity to the passions of the soul.” (p.71) Recognising these qualities of emotions leads in at least two directions. Firstly, it chastens expectations about how much the passions are voluntary, and leads to realism about to how quickly they can be (re)directed. But secondly, it suggests means by which we can tutor our passions. In this area, the notions of habitus and virtue with which Aquinas worked are helpful. More on this to come later.

Summary

This has been a very high-level summary of Aquinas’ psychology, with much omitted. But there are a number of recurring words that we have seen that highlight the key elements of the way Aquinas presents his map:

• holistic: the body-soul relation inheres throughout the complete human person, the soul being the principle of life throughout and accounting for all living powers, not just our rationality.
• tiered: human psychology has a number of layers, not just rational and non-rational but also a semi-rational zone in which the passions are located. This layer, corresponding in some ways to the modern notion of the subconscious, is not under the simple control of the rational faculties but responds directly to sense experience. But is influenced by the rational powers both in a modulating way (influencing a given motion of the passions in restraining or animating directions) and in a conditioning way (shaping the instinctual movements of the passions by gradual training).
• plasticity: the movements of the semi-rational middle layer are conditioned by the body and therefore can be shaped significantly not just by bodily conditions, but by the enduring configuration of the body. The findings of neuroscience have identified brain topography as the locus for this configuration (“neurons which fire together wire together” ). It is this plasticity of the body that permits the training of the passions, for good and ill.

Note that what we have done here (following The Logic of the Body) is not yet an analysis of Aquinas’ psychology or a direct contrast with emotional voluntarism, but rather a summary of the defining concepts of his approach so as to lay a foundation for critical appropriation. I’ve focused on just trying to make clear those key concepts that La Pine takes up in his own constructive work later.

I confess that while reading this description of Thomistic psychology I kept returning to the (simplistic?) question: is it actually true? Does it correlate with anything observed that justifies it, and not just in general terms: is there reason to think the specific layers and powers of the soul Aquinas describes are real? Or is it a positivist-model kind of true; not necessarily corresponding to (material?) realities, but useful for prediction? As the complexity of the model grows, so does the evidence required to substantiate it, and at some point the epicycles become so involved as to cast doubt on the whole edifice.

On the other hand, complex phenomena rightly require complex explanations, and I think La Pine shows enough points of contact between Aquinas’ account and the observations of modern neuroscience to assuage this concern. And after all, his starting point was that other theological models of human psychology fail to account for all the details – offering a more involved account is his goal. Aquinas’ intricate thinking yields concepts that aid in the task of theologically describing what medical science and everyday experience testify to being intricate.

1. It is more and more my experience that when I’m reading some past giant who says something that is at first glance obviously wrong, on reflection it actually brings to the surface some submerged aspect of my modern mindset, which on being examined rather than assumed appears distinctly less worthy of assumption.
2. Contrast this with Descartes’ separation of soul and body into two complete substances in themselves: the body becomes a tool or instrument of the soul, which can be roughly identified with the mind. The problem for the dilemma raised above should be obvious: to which side of the separation do the emotions belong? The body or the mind/soul? It also needs to be pointed out that Aquinas does think the soul can subsist without the body, as an “incomplete” substance, which is true of humans in the intermediate state.