Aristotle gave two principles making a person: a soul and a body. St. Paul, perhaps taking a cue from Plato, gives three: soul, body, and spirit. We can see these accounts as compatible in different ways, but the way that most interests me is by considering that Aristotle’s account of man is taken in the line of what is proper to nature whereas the biblical/ Platonic account requires more than what is proper to nature.
Aristotle’s account of human beings is taken from a book that is part of a larger project of the study of nature, but what Aristotle calls a nature is essentially a principle of motion. Even where the operation of the soul is not a motion (and vital operations are not motions as Aristotle defines the term) he is still chiefly interested in operations so far as they relate to motion and change – sensation explains the animal’s way of getting around the world, and reason is treated so far as it relates to sensation – which is why Aristotle only explains those parts of intellect that relate to the sensible world. But in man there is in addition to this a principle that does not formally relate to motion, but to the immobile, unchangeable, and eternal, that is, the divine. There are some indications that Aristotle recognized this, and he would have seen the need to develop the nature of the principle outside of natural science as such. Taken in this way, we need not regard his account of man in De anima as exhaustive, but as exhaustive of man as a nature, that is, a being that relates intrinsically to the mobile.
Again, form and matter are only of value to one who is questioning about the possibility of motion, that is, a process that is incomplete while on going. For one who is not puzzled by (or at least questioning) motion and becoming, matter and form are only answers to a questions he is not asking. In the measure that one finds immobile realities in nature, matter and form are not the best concepts to turn to. For this reason, there will be problems to address when we use matter and form to explain knowing, life, or even the relation that things have to things that know and are alive. This is not to deny the usefulness of the matter/form binary when explaining these things, but it will more explain them so far as they relate to the mobile, and not so far as they are immobile. So far as we consider life as complete at any moment of the one living, or knowledge as perfect at every moment of the knowing, or anything so far as they are relating to life or knowledge considered in this way, matter and form are not the best binary. We need another reality above and beyond these things – a reality that by its very nature transcends motion and so transcends nature. Spirit suggests itself as an ideal name for such a thing.
Note that, on this account, we have reason to extend the notion of spirit to include even the natural world so far as it is knowable. Spirit in this sense appears to be form so far as it rises above the mere potentiality of matter, and this is the source of the knowability of things, even to sensation.
Spirit can also be considered as synonymous with self. Taken in this way, we could consider matter and form as parts which are used by the self. My soul and my body are principles of my operation, not the self as self. Taken in this way, spirit seems to mean life so far as it is opposed to nature.
Just Thomism 
01010101 said,
December 27, 2011 at 11:38 am
Well, yes a realm of Spirit, Nous, Mind would help out matters philosophically speaking (overlooking how..spirit supposedly interacts with matter, or “substance” for that matter)–so, then perhaps put on the Soul-o-meter and show us –an EEG suggests otherwise (IMO, Aquinas at times seems to ….rely a bit on the Augustinian-ghost when Aristotle’s old…naturalist system can’t quite justify the theology (like.. a monotheistic .”God”). That s how judeo-chr.-islamic dogma works. Some almost-truths with…priestly mysteries
Crude said,
December 27, 2011 at 4:03 pm
Stimulating post as always. I hope you had a Merry Christmas. You should really police your blog more – it’s one of the most thoughtful and polite blogs around, a shame to have that soiled.
Nightingale said,
December 27, 2011 at 11:09 pm
In St. Thomas’ commentary on First Thess 5:23 (where St. Paul says spirit and soul and body), he says that spirit refers to intellectual powers and soul refers to sensitive powers. Since the intellectual powers are the ones by which a person is constituted, perhaps that’s why one would call the spirit the “self”.
James Chastek said,
December 28, 2011 at 9:07 am
Here is the passage. My post is a variation on the same idea. STA divides spirit and soul as immateriality and sensuality, I divide them as one and the same power in its orientation to immobile and mobile things.
Commentary on ut integer spiritus vester, anima, corpus… servetur. sc. “that your spirit, soul and body might be preserved [for the coming of Christ].
Some take these words as an occasion to say that in man one thing is spirit and another soul, placing two souls in man – one which animates and another which reasons. These things are condemned in the teachings of the Church. And so it should be understood that these do not differ according to essence but according to power. For in our soul there are some powers, like the sensitive powers which are the acts of corporeal organs; others that are not the act of corporeal organs, but are separated from them, like the intellectual parts. And these are called spirit as if immaterial and in some way separate from matter, inasmuch as they are not the act of a body (they are also called mind, as is said in Ephesians IV 23: [be transformed] by the renewal of your mind) but inasmuch as they animate, they are called soul, because this is proper to them. And Paul is speaking properly here. For three things run together to make a sin: reason, sensuality, and the execution of the body. And so Paul wishes that there should be sin in none of these…
Occasione enim verborum istorum dixerunt quidam quod in homine aliud est spiritus, et aliud anima, ponentes duas in homine animas, unam quae animat, aliam quae ratiocinatur. Et haec sunt reprobata in ecclesiasticis dogmatibus. Unde sciendum quod haec non differunt secundum essentiam, sed secundum potentiam. In anima enim nostra sunt quaedam vires, quae sunt actus corporalium organorum, sicut sunt potentiae sensitivae partis. Aliae sunt, quae non sunt actus talium organorum, sed sunt abstractae ab eis, sicut sunt potentiae intellectivae partis. Et hae dicuntur spiritus, quasi immateriales et separatae aliquo modo a corpore, inquantum non sunt actus corporis, et dicuntur etiam mens. Eph. IV, 23: renovamini spiritu mentis vestrae. Inquantum autem animat, dicitur anima, quia hoc est ei proprium. Et loquitur hic Paulus proprie. Nam ad peccandum tria concurrunt: ratio, sensualitas et executio corporis. Optat ergo, quod in nullo horum sit peccatum. Non in ratione; unde dicit ut spiritus, id est, mens vestra, servetur integer. In omni enim peccato ratio corrumpitur, secundum quod omnis malus est ignorans. Item nec in sensualitate, unde dicit anima. Item nec in corpore; et ideo dicit et corpus. Hoc autem fit sic, quando servatur immune a peccato.
James Chastek said,
December 28, 2011 at 9:47 am
St. Thomas’s account is very proper here, as he points out himself: Paul commends his readers that God might sanctify them, and that they might be kept morally pure, and then (by STA’s account) he lists those three powers in man that we distinguish when we ask the question “what parts in man can sin” and so, by way of opposition “what parts can be kept pure from sin?”
01010101 said,
December 28, 2011 at 10:39 am
Actually I agree Paddy Chastek–it’s a shame that you allow Randians and machiavellians pretending to be catholics pollute your blog with their opportunistic drivel. Why if the Feser gang had its way, only GOP and glibertarians would be allowed online.
And however troubling to phony zealots it may be, the philosophical issue of interaction remains (as much as it does for Descartes).