Conclusion: The soul is the single unified principle of all its faculties and their activities.
The Shaykh offers two proofs for the above, the first of which (see below) is a disjunctive syllogism whose (logical) form is as follows: either (a) or (b); but (a) is false; therefore, (b).
Take, he has as assume, the following as an undeniable datum of common experience: Zayd sees some object x and then becomes angry as a result. This is a unified experience in which Zayd’s activities of seeing and being angry are obviously interrelated.
Now, if the faculties of the soul – in this case the faculties of sight and irascibility – did not have a single principle (mabda’), then when one of them (e.g., sight) is affected or actualized by its corresponding object, their interrelation with each other must be explained in one of two ways:
- (a) The other faculty (i.e., of irascibility) is also affected by the same object (i.e., x) as the first faculty, which entails that a single faculty, i.e., the power of irascibility, would perform two distinct activities, namely, seeing and anger. Or
- (b) Both faculties are related to a single principle which unifies their activities/operations.
The Shaykh states the above distinction more clearly when a little further in the text he writes (tr. Rahman):
In fact, since these faculties [i.e., of sight and irascibility] interact and influence each other, either each of them must change with the other’s change [i.e., option (a)] or there is one single entity which unifies them [i.e., option (b)]; […].
Then, he refutes option (a) by drawing on certain premises which he proved earlier (see, chapters II and III). The gist of that refutation is his claim (tr. Rahman, my emphasis):
Not every faculty is suited to every activity; the faculty of [irascibility], [qua] the faculty of [irascibility], does not [see], and the faculty of [sight], [qua] the faculty [of sight], does not become angry.
Therefore, he concludes, option (b) is the case.
But then he takes up an objection in which someone modifies option (a) so as to explain the above datum of experience (i.e., Zayd seeing x and becoming angry) but in a way that would avoid positing a single unifying principle (i.e., option (b)). The objection basically states:
(a*) when Zayd sees x and become anger, it’s not that the object of his vision, x, also affects his faculty of irascibility such that it perceives x and then produces anger in him; rather, it’s that whenever Zayd sees x, that experience is necessarily followed by the experience of him becoming angry. But, again, this is not because the object of his faculty of sight directly affected his faculty of irascibility. In Zayd’s perceptual experience, the objector maintains, there’s only the succession of seeing x by becoming angry, nothing more.
The Shaykh responds by noting that (a*) would entail two consequences both of which are false, then concludes back to (b). He reasons, I think, as follows:
There’s undoubtedly a relation between Zayd’s (act of) seeing and (act of) becoming angry. This means his faculty of seeing has some sort of an effect or influence on his faculty of irascibility – for again, his experience is that his anger results from first seeing x, not the other way around. Now this relation, given in experience, between his two faculties is either in terms of:
- (c) the causal role of the object of his faculty of sight, or
- (d) in terms of something other than the causal role of the object of his faculty of sight
If (c), then that means that his faculty of irascibility is causally affected by the object his sight i.e., x; and this would entail that that faculty would perceive x. For that is just what it means for any given faculty to be causally affected by an object, i.e., it means for it to perceive it. But if his faculty of irascibility perceives x, then we have the same problem as above with option (a), i.e., that one faculty qua one will have two distinct activities, i.e., of perceiving x and becoming angry. This has already shown to be false – a single faculty can’t have two distinct activities.
If (d), then it will follow that Zayd’s anger is not in fact due to his seeing x. And this contradicts the initial assumption that it was in fact due to seeing x. In other words, it cannot be the case, as the opponent maintains, that Zayd becomes angry as a result of seeing x but not because of a causal relationship between the object (i.e., x) of his faculty of sight and his faculty of irascibility. That, as the Shaykh says, is a contradiction. If we agree that he becomes angry be-cause of seeing x, but then hold that the object of his seeing is not what affects his irascible faculty (so that it produces anger in him), then he simply did not become angry be-cause of seeing x, which contradicts our initial assumption that he in fact did so because of seeing x.
Therefore, concludes the Shaykh, option (b) is the truth, i.e., that the faculties of sight and irascibility have a single principle, i.e., the soul, which unifies their activities into one coherent experience.
This is the end of his first argument for the above conclusion. And God knows best.