Thomas Aquinas
Disputed Questions on the Mind
Article 12
Is the mind the same as its powers?
[Translation note: I translate 'anima' as 'mind', but by that, I do not mean to exclude animal minds. On the contrary, I mean to include both the sentient minds of animals, and the rational minds of humans.]
With regard to this question, it should be said that there are diverse opinions. Some say that the mind is [the same as] its powers, but others deny this, saying that the mind's powers are certain properties of it.
In order to understand the differences between these opinions, I should point out that a power is nothing other than the source [principia] of some operation, be it an operation that is done or an operation that is undergone. But the 'source' I am speaking of is not the agent or recipient [of the operation]. Rather, it is that by which the agent acts or that by which the recipient undergoes [the operation in question]. For just as the builder's skill is the power in the builder by which he builds, so also is the heat in a flame that by which the flame heats [other things], and dryness is the power in a log [by which it is combustible], for things are combustible insofar as they are dry.
Thus, those who postulate that the mind is [the same as] its powers understand this to mean that the very essence of the mind is the immediate source of all the operations of the mind, saying that a human understands through his or her mind, a human senses and [performs] other such operations [through their mind], and the mind is given diverse labels according to the diversity of these operations: [it is called] the 'sense' [or 'sentient power'] insofar as it is the source of sensation, [it is called] the 'intellect' [or 'intellective power'] insofar as it is the source of understanding, and so on for all the other [operations for which the mind is the source]. Whence, we label the heat in a flame as its power to heat, melt, and dry other things because it performs all of these things.
But this opinion cannot stand. First because everything that enacts anything --- and here I mean to refer to the thing which acts --- it does so only insofar as it is actual in the way [in which it acts]. For a flame heats not insofar as it is actually bright, but only insofar as it is hot, and hence every agent brings about something similar to itself. Whence, it is necessary that that by which something acts be considered as the source by which it acts, for it is necessary that each be in conformity. Thus, in book II of the Physics, it is said that the form and the generator are the same in species. Therefore, when that which acts does not pertain to the substantial being of the thing, it is impossible that the source by which it acts is something of the essence of the thing, and this is obvious for natural agents.
For when it comes to generation, a natural agent changes matter into form, and that happens because the matter is first disposed to that form, and eventually the form follows, according to which generation is the terminus of the alteration. It is necessary that, on the part of the agent, that which immediately acts is an accidental form corresponding to the disposition of the matter. But it is necessary that the accidental form acts in virtue of the substantial form, as an instrument of it, so to speak (otherwise, it would not induce a substantial form by acting).
On account of this, the only apparent source of action in the elements are their active and passive qualities, which nevertheless act in virtue of the substantial forms [of the elements]. Consequently, their actions are not directed only to accidental dispositions, but also to substantial forms. For in the making of artifacts, the activity of the instruments are directed at the form intended by the artist.
But if some agent were, by its action, to directly and immediately produce a substance (just as we say of God, who by creating produces the substances of things, and just as Avicenna says of the Agent Intellects, from whom (according to him) the substantial forms of inferior things flow), an agent of this sort would act through its essence, and in that case, its active power would not be distinct from its essence.
But regarding passive powers, it is obvious that a passive power for a substantial act belongs to the genus of substance, and a passive power for an accidental act belongs to the genus of accident --- by reduction (as a principle rather than as a complete species). For every genus is divided into potentiality and actuality. Whence, a human belongs to the genus of substance, and a human's potential whiteness belongs to the genus of quality.
However, it is clear that the powers of the mind, be they active or passive, are not spoken of directly with respect either to something substantial or to something accidental. Similarly, a being that is actually intelligent or sentient is not actually intelligent or sentient in a substantial sense, but rather in an accidental sense, to which the intellect or sense are directed, and similarly, to be large or small, to which the power of growth is directed.
But generative or nutritive powers are directed towards producing or conserving a substance, though through changing matter. Whence, such actions, just like all the other actions of natural agents, come about by a substance through intermediate accidental principles. Whence, the powers of the mind are not [the same as] the very essence of the mind, but rather are properties of it.
Thereafter, it is apparent from this that from the diversity of the mind's actions that they belong to diverse genera, and they cannot be reduced to one immediate principle, for certain of them are actions and certain of them are passions, and other of them differ by further differences, which differences must be attributed to diverse principles.
And so, since the essence of the mind is a single principle, it cannot be the immediate principle of all of its actions. Rather, it must have many diverse powers that correspond to the diversity of its actions. For a power is said to be correlative to its act, whence according to the diversity of actions there must be a diversity of powers.
Hence, the Philosophy says in Ethics VI that when it comes to things that belong to the mind scientifically (i.e., when it comes to those features that we identify by our scientific investigations of the mind), those things belong to the mind necessarily, whereas the things that belong to the mind's ratiocinative features belong to it in a contingent way, and so these two classes of things must be reduced to diverse powers, for things that are necessary and things that are contingent differ in kind.