The Incorruptibility of The Subsistent Soul According to Thomas Aquinas
Kevin I Flannery FAITH Magazine March - April 2008
In question 75 of the first part of the Summa theologiae[ST 1.75], Thomas Aquinas puts forward an elaborate argument for the incorruptibility of the human soul, interweaving ideas from Aristotle’s Categories[ Cat.], De anima [ De an.], and Metaphysics[ Metaph.], and possibly also from Plato. But although the argument is elaborate, Thomas’s basic thesis can be stated succinctly: the soul is by nature incorruptible since it is both subsistent and its operation is ultimately independent of the body.
Thomas takes his conception of subsistence from Cat. and Metaph. v,8. In chapter 2 of the former, Aristotle says that some things are “in” things and some things are “said of” things, the former being accidental properties (as when white is found in Socrates), the latter essential properties (as when ‘man’ is said of Socrates). Sometimes accidents are in other accidents, as when we say that Socrates is a ghastly white; and sometimes essential properties are said of other essential properties, as when ‘animal’ is said of ‘man‘. But a substance, says Aristotle in chapter 5 of Cat., in the proper sense is neither in, nor is it said of, another thing; it is, so to speak, at the bottom of the stack of things “in” or “said of”. Substances in this proper sense are “separate”.Unlike accidents and essential properties, which cannot exist without an ultimate subject, they are ultimate subjects in their own right. If we want to indicate a white thing or a man, we have to point to something like Socrates; but if we want to indicate Socrates, we point to Socrates. He is a concrete object of reference.
In Thomas’s way of speaking, this is to be subsistent; and, as we have seen, he maintains that the human soul is subsistent. But a soul is not subsistent in quite the way Socrates is. Although a soul is subsistent in the sense that, when we refer to Socrates’s soul, we refer to him, a soul is just a part of the composite thing, that is, a part of the composite of soul and body, which is, for example, Socrates. To many people, this will smack of “dualism,” often associated with Plato. But Thomas’s approach has a solid foundation in Aristotle, as he himself points out in ST 1.29.2. In both Cat. v (3a29-32) and Metaph. v,8 (1017b12-13), Aristotle acknowledges that a part of something can be substance: a part of something (such as a hand) is not “in” a body in the way white is but in away that allows it to be found at the bottom of a stack of accidental and/or essential predications, as when we say that a hand is a limb or an instrument or whatever. In other words, also a part can be subsistent.
In the second book of the De anima, in a remark that anticipates his claim in Book three that a part of the soul (the intellect) is separable and immortal, Aristotle appears to allude to the sort of Platonic dualism that he would reject. He has been setting out his basic position that the soul is the actuality of a body and that, therefore, certain functions (“parts”) of the soul are inseparable from its body, such as, its nutritive function. But then he says: “Yet nothing prevents some parts from being separable since they are not the actualities of any body. Moreover, it is unclear whether the soul is the actuality of its body in the way that a seaman is of a ship” [ De an. ii,1,413a6-10]. In his commentary on the De anima(and also elsewhere), Thomas interprets this as a referenceto Plato. The idea would be that Aristotle is suggesting that a subsistent and separable part of the soul is a possibility (this would be the intellect) but that its presence in the composite person need not be like that of a seaman in a ship. Although Plato nowhere employs that exact image, he does speak of the soul as residing in the body as if in a prison and of the body as the sepulchre of the soul (see Phaedo62B3-4, Gorgias493A2-3, and Cratylus400B11-C10).
In ST 1.75.2, which asks “whether the human soul is something subsistent,” the first objection argues that any subsistent thing is a “certain something” [ hoc aliquid] and that, since a certain something is a composite of soul and body, the soul cannot be a certain something. Thomas’s reply is that something can be a certain something in two ways: either as a complete subsistent individual of a species (as Socrates is of the species man), or in a more generic sense that does not exclude parts, incomplete as they may be, from subsistence. A hand, he says, is subsistent in this latter way; so also is the human soul. Thomas is treading the middle way he sees in De an. ii,1, maintaining that a part of the soul might be subsistent, without failing to be a genuinepart of the soul that isthe form of its body. Sometimes he speaks of the soul using the body as if using an instrument – not an extrinsic instrument, however, as when a seaman steers a ship, but as an intrinsic one. This is to say much the same thing as that the soul is subsistent but as a genuine part: the directing part of the complete person, who is made up of soul and body.
Is it Subsistent?
But what are Thomas’s grounds for maintaining that the soul – that is, the rational soul – is subsistent even in this mitigated sense? He maintains this on the grounds that the soul as suchhas its own operation. Even this idea Thomas takes over from Aristotle, who says in the first chapter of the De anima, “If there is something among its actions or passions that is proper to the soul, it [i.e., the soul] will be capable of a separate existence” [403a10-11]. Aristotle is here anticipating his discussion of the intellect (active and passive) in De an. iii,5. Thomas holds that, when Aristotle speaks in De an. iii,5 about separability, he is speaking about the whole intellect: that is, the so-called “active intellect” and “passive intellect”.
The arguments that Thomas offers for believing that the rational soul’s operation is intelligible in itself – that is, without introducing anything extraneous such as the body or the senses – almost all derive from Aristotle; and they are not, on first reading, terribly convincing. One of them – in fact, the lead one in the article arguing for the soul’s subsistence – is quite inextricably bound up in Aristotle’s very crude physiology of perception. Thomas follows Aristotle in maintaining that the intellect becomes all things, which is to say (among other things) that its object is not limited in the way the sense of sight is limited to the visible, hearing to the hearable, and so on. It must be allowed, Thomas says, that the intellectual operation of the soul is both incorporealand subsistent.
For it is obvious that man, by means of the intellect, can know the natures of all corporeal things. Now whatever is capable of knowing certain things cannot have any of them in its own nature, for that which is present in it naturally would impede the knowledge of other things. And so we observe that the tongue of a sick man that is infected by a choleric and bitter humour is incapable of sensing anything sweet, but everything seems to him bitter. So, if the intellectual principle contained in itself the nature of some body, it would be incapable of knowing all bodies [ ST1.75.2].
So Thomas, following Aristotle (see De an. ii,10,422b8-10), thinks that the cause of all things tasting bitter to the sick man is itself bitter. Obviously, this cannot stand and Thomas’s position receives no support from that quarter.
But pointing out that Thomas’s physiology is antiquated does nothing to impugn the basic insight that there is a difference between the intellect and the senses that has to do somehow with the intellect’s being less directly linked to the physical world than are the senses. When a man grows ill (in the relevant way), something physical does affect the way his tongue tastes things. When something physical (such as fatigue) affects the intellect’s operation, it does so in a different manner, for the intellect can still know thatit is being affected in this way, thereby showing that its operation is independent of the physical factors. Or, if it is not completely independent, it certainly has the ability to stand over and even to rise above the physical factors that is absent in thesenses. The tongue has no choice but to go on tasting all things as bitter; this will only change once the physical situation has changed.
In ST1.75.6 Thomas explains that the intellect is not subject to contraries, as are physical things: a stone, for instance, becomes cold if warmth is driven away, warm if cold is driven away. Although contraries enter into the intellect (it “becomes” them), they do not do so as contraries, for a contrary always drives out its counterpart. As Aristotle says often and as Thomas repeats in ST1.75.6, there is “one science of contraries” – which is simply to say that the intellect stands above such physical processes. It can grasp both cold and hot precisely because it will never have either of them in its nature as contraries. Its operation is intellectual, not physical.
Is it a non-physical principle?
Returning, though, to ST1.75.2, just after discussing the sick man’s tongue, Thomas argues that the intellect does not even make use of a physical organ [ ST1.75.2]. His argument proceeds analogically. Presupposing that the pupil of the eye when it sees a colour becomes that colour (i.e., becomes coloured), Thomas notes that, if its object is a coloured flagon, the flagon’s colour will impede the pupil’s picking up certain colours. Water poured into a red flagon, for instance, will appear red. Similarly, if the intellect (which “becomes all things”) depended on a physical organ, like the red of the flagon, that organ’s physical characteristics would impede the intellect’s ability to “understand” certain physical characteristics of things. But this would mean that theintellect was not capable of understanding all the physical characteristics of things; and so, Thomas concludes, the operation of intellect is not tied to a physical organ.
This argument bears with it a familiar problem: because he is following Aristotle (see De an. ii,7,418b27-29, iii,2,425b22-25), Thomas’s physiology is suspect, for he supposes that, when sensing a colour, the pupil of the eye becomes that colour; and that presupposition vitiates the force of the argument. Perhaps one could argue that, in so far as certain light waves get to the retina and are there processed, etc., in a sensethe eye does become coloured; but the damage has already been done: the Aristotelian theory sounds a bit too much like the theory of bitter humours infecting the tongue. But even if Thomas’s physiology is (from our perspective) wobbly, we can acknowledge that he is again on to something: understanding (for instance) colours is different from sensing colours.There is a sort of distance which would not be there if the operation of the intellect were tied essentially to a physical organ. Changing the physical characteristics of a sense organ might change whatwe perceive, but it seems right to say that changing something physical could not change howwe see – it could not, that is, change the operation of the intellect itself.
Dependence upon the Physical
Or could it? We know that injuries to the head can affect one’s capacity to think and that changes in dopamine levels in the brain can have bizarre mental effects. In De an. i,4, Aristotle in fact anticipates such objections, at least in principle. Thomas’s interpretation of Aristotle’s remarks gives us a good idea how he would answer objections about blows to the head and dopamine levels. In De an. i,4, Aristotle argues against those who maintain that the soul can be in movement. These people argue that the soul itself is pained and pleased, perceives and thinks [408b1-3]. Since these are ways of moving or being moved, the soul too must be moved. Aristotle replies that it would be better to say that it is the man(i.e., the composite of soul and body) who is pained andpleased, perceives and thinks, even though there is a certain sense in saying that the soul does these things since the movement originates in the soul [408b7]. He mentions in this connection changes in the body that affect the way we think, such as old age and the consumption of drink. Such things do not affect the soul, he says, but “its vehicle” [408b23], the composite man. He finishes this section by remarking that intellect is “a more divine and impassible thing” [408b29] – that is, than the composite in which it is found. That is his usual prelude to saying that it is capable of separate existence.
Thomas is not entirely comfortable with all the ideas expressed in this section of the De anima. An objection in ST 1.75.2 maintains that, if, as Aristotle says, the soul does not feel and think, it has no proper operation and so it cannot be subsistent. Thomas’s first reaction is to say that Aristotle is not speaking in his own voice but in the voice of those with whom he is in dialogue. But he then relents and acknowledges that sense can be made of the remarks in their own right. He notes once again that there are two ways of being subsistent, only one of which – the properly subsistent – excludes being a part. He readily acknowledges that it is the composite, and not the soul, that is subsistent in the primary sense, so that it is also to the composite that the operation of theintellect is properly attributed. But still, the soul (the rational soul) doeshave its proper operation since it is the origin of the thinking done by the composite whole.
Thomas does not apply this set of ideas to the problem of old age and drunkenness; and, indeed, in his commentary on that section of Aristotle, he again argues that Aristotle is speaking in the voice of his interlocutors. But it would be consistent with his overall approach to say that any changes to the operation of the intellect effected by old age or drunkenness – or, for that matter, altered dopamine levels – ought to be attributed not to the operation of the rational soul itself but to the operation of the composite man. When Thomas does discuss the type of thought engaged in by the separated soul, he acknowledges that it is different from that of the soul when it was part of the composite man; moreover, it is different becauseit is no longer a part of the composite man (see ST1.75.6 ad 3; also ST 1.89).
Is it Incorruptible?
This brings us to a final, but central, question: But how do we know that a subsistent thing is not corruptible? Thomas’s answer to this question (in ST1.75.6) sounds occasionally like the position Plato sets out in the Phaedo, where the character Socrates argues that the concept of the soul – and, presumably, also its being – is so tied up with life as not to admit of its opposite, death [105C8-E10]. Does the fact that a position is found in Plato necessarily mean that it could not have been held also by Aristotle? Aristotle’s statement at De an. i,1,403a10-11 that, if a part of the soul has its own operation, it is capable of separate existence, requires an explanation of some sort; something like the position in the Phaedofits the bill.
In any case, Thomas argues that something which is in itself ( per se) subsistent, if it is to perish, must perish in the same way: in itself. He has already argued (in ST 1.75.2) that a concrete man is subsistent in himself: he is a whole independent thing, not dependent on any other thing, as an accident is dependent on the subsistent thing in which it inheres. When a man dies that whole thing dies; that is to say, that subsistent thing, made up of body and soul, perishes as the soul is separated from the body. But the soul is also subsistent in itself, although in a different way – or ways. For one thing, it is subsistent as a part of the composite man, but it is also subsistent in so far as its operation is independent of the body. This gives a man’s soul a type of subsistencenot enjoyed by a brute animal’s soul since the operation of a brute animal’s soul is inextricably tied up with its body and so ceases not only to operate but also to be when the composite animal perishes. This cannot happen to the human soul, says Thomas, since it is just form and you cannot take form away from form. For something to perish is for something to be separated from something, but in this case there is only form – and nothing to take it away from, or to take away from it. Being, therefore, is intrinsically bound up with a subsistent form, since there is nothing in the latter – or linked to it – that could possibly cause it to cease to be. This is the bit that sounds like Plato; but, whether it is Platonic or Aristotelian or both or neither, it is Thomas’s primary basis forasserting that the human soul is incorruptible.
One point needs to be added, however, before finishing – a point that some may find surprising. Although Thomas does (obviously) hold that the human soul is incorruptible, he does not deny that it could go out of existence. In his answer to the second objection in ST1.75.6, he acknowledges that God could simply cease to sustain a soul in being. But this would not be for the soul to perish (or to corrupt) since to perish means to go out of existence because of something in the nature of that which perishes. When we say that something is perishable or corruptible, we are speaking about its nature. When a brute animal perishes, it does so because its nature is such that, when its body corrupts, it perishes. We have seen that a subsistent form such as the human soul has nothing in itthat would allow such an event. But when God ceases to sustain something in being, the cause of its not being is not in itself but in God. Such an event is not a perishing or a corruption but, as Cardinal Cajetan says in his commentary on ST1.75.6, an annihilation. And the annihilation of even a subsistent soul is well within the power of God.