Undoubtedly St. Thomas thought like you say. It is quite normal. Still those concepts are mental constructs which were the result of an elaborated and uncommon thought process. Those are typical high order relations which we cannot even imagine. Invented to explain the existence of beings of which we have never have had any experience, how could we be able to associate to them any accessible reality?
I am only describing how Aquinas came up with the idea. In fact, the
esse/
essentia distinction is also necessary in order to explain the diversity of species of beings, so we could justify it based on principles that are ultimately derived from experience.
<…> This is very interesting for the phenomenology of relations: When you say that we have to make necessary adjustments to think of “actus essendi and essence as act and potency” the expression “necessary adjustments” makes sense to me. To me it is about a kind of movement that we initiate but don’t complete. How would you characterize that necessary adjustment (and I am not referring to the result but to the process)?
The idea is as follows: what is the easiest kind of act-and-potency to understand? The actions, or operation, produced by a supposit. (Like when I get up and walk around, or what have you.) That forms the paradigm on which other act-and-potency paradigms—applied to other kinds of composition—are based.
Hence, we have accident-substance, where accident functions as the “act”*and substance as the “potency.” (Accidents are the perfection and fulfillment of substance.) But you can see that although “accident,” like operation, perfects the potency it is composed with, that there is a difference: namely, accidents are immanent to the supposit, whereas operation is transitive.
So I will permit myself to get a little technical here. We are using a logical technique here called
analogy of proportionality. It is the classic analogy, the kind you find in the Millers Analogy Test or on the SAT to test your understanding of vocabulary:
As operation perfects the supposit,
in a similar way, accident perfects substance. Or, if you like: operation : supposit :: accident : substance.
But by the very fact that we are using analogy, there must be a
difference between the two compositions: otherwise, there would be no analogy.
The aspect that is the same, we call the
res significata, the thing (understood in the most generic sense possible) that is signified. The aspect that is different, we call the
modus significandi (literally “manner of signifying”), the way in which it is signified.
In this case, the
res significata is the notion of perfection: both compositions imply a perfection, or fulfillment, of one of the components.
The
modus significandi, however, is different. In one case, the perfection is transitive (it has an effect on other beings, or at least on other parts of the same being); in the other case, it is strictly immanent.
Whenever we make an analogy, there is always the same process: affirmation of the
res significata found in the previous pair of terms, and denial of the
modus significandi found in that previous pair.
I can do a similar thing thing with prime matter and substantial form: the substantial form still perfects the matter, as in the other cases; and like the accident-substance composition, this one is entirely immanent (
res significata). However, there are a number of differences: the potential component—the prime matter—is not subsistent; it has no independence without the form; indeed the prime matter is co-created together with the form; the form does not merely perfect the matter, but defines what kind of being that creature is.
Finally, I can do a similar thing with
actus essendi and
essentia. As with the others, I can affirm (
res significata) that the act of being perfects the essence; that (like prime matter with respect to form), the essence is co-created together with the act of being; and that the composition is completely immanent. However,
unlike the other act-and-potency pairs (denial of
modus significandi), the role of the act of being is to be the source of being for the entire supposit. The essence is a potency, but in no way does it pre-exist before the act of being; rather, the essence’s role is to limit and define the act of being (hence making the creature the kind of being that it is).
So that is the process: you start with the easiest kind of act and potency to understand, and work your way up to the most difficult one, by affirming the appropriate
res significanda and denying the
modus significandi, as appropriate.
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