“the division of act and potency” as a reflection of power, iii

St. Thomas on the terms “actus” (here “act”) and “potentia” (here “power” but usually translated as “potency”):

[W]e must observe that we speak of power in relation to act. Now act is twofold; the first act which is a form, and the second act which is operation. Seemingly the word ‘act’ was first universally employed in the sense of operation, and then, secondly, transferred to indicate the form, inasmuch as the form is the principle and end of operation. Wherefore in like manner power is twofold: active power corresponding to that act which is operation—and seemingly it was in this sense that the word ‘power’ was first employed:— and passive power, corresponding to the first act or the form,—to which seemingly the name of power was subsequently given.

Power was first said in relation to operation. The first sense of “power” or “potency” or “potential” is as that which underlies operation. This is the same thing as the nature or habit, but it is considered so far as it is perfected by operation, and so is seen so far as it is imperfect. The Scholastics called this habit or nature that operation perfects “first act”, though it could also be called “second potency”. Hence, we stumble on the sticky problem: are “things” acts or potencies, imperfect or perfect? Neitehr answer works: They are composites. What we call things are unavoidably middle-states between pure potency and operation, and as such they can be named in relation to either extreme.

Consider a chef who knows how to make soup. Which is the actual or potential, the chef or the soup? In one sense, the chef actualizes soup, and in another sense, the soup actualizes he chef. One and the same power, ability, or habit is both actualizer and actualized; the very same power is both perfecting and perfected in different ways. This is simply the paradoxical nature of natures (or habits- like “being a chef”- which are “second natures”).

People generally fail to appreciate the significance of hylomorphic theory referring to things both as “potencies” (namely, as “second potencies” as opposed to first potencies)  and as “acts” (namely, as “first acts” as opposed to second acts or operations) The consequence of this is that “causality”, when said of any hylomorphic thing, always involves some kind of dependence on another too: which is simply to say that any causality by a hylomorphic entity requires that it be also in some way an effect. Hylomorphic things do not just cause things to exist, (and therefore produce that which depends on them to exist); it is also the case that the very causality they exercise depends on the effect qua object and so and is perfected by it. This is one of the more subtle senses of “everything in motion is being moved by another”. In light of hylomorphic composition, we can even say “all physical causality is being caused by another”. Indeed, a physical cause that was not caused by another would not be perfected by its object, which is ridiculous. To be clear “a nature or habit that brings X forth” both brings X into existence, and is at the same time brought to it perfection or completion by actually bringing forth X (whether X is some operation or “thing” is of no importance here).

So far- and this is important- we are firmly locked within the physical world and are therefore doing physics of one kind or another. We said “physical cause”, but as far as we know these are the only causes that exist. All causes are being caused by another, and that’s it. What sense can there be in speaking of a cause that is not perfected by its object? God either had the ability to create the universe, or not, if not (put your own contradiction here) if so, then this power was perfected and completed by the actual universe. Either way, there is no purely uncaused cause.

But all this is forgetting what we were talking about. Causes are caused by objects precisely as hylopmorphic (or, if there are creatures other than physical ones, by their composition).  It is the composite nature of what we call “things” that makes it impossible for any thing to be an uncaused cause. Hylomorphic composition is exactly what is needed to account for the strange and limited causality of the things we find around us.


  1. December 4, 2009 at 7:18 pm

    “People generally fail to appreciate the significance of hylomorphic theory referring to things both as “potencies” (namely, as “second potencies” as opposed to first potencies) and as “acts” (namely, as “first acts” as opposed to second acts or operations)”

    I suspect that the lack of appreciation is the tendency among many Thomists to want their words to be “language bricks” or “logical bricks”, univocal terms that maintain their same meanings no matter the context in which they are used. Thus they have difficulty conceding that something is both in act and in potency. Perhaps they are Thomists in their conclusions, but Scotists in their method.

    By the way, James, this is Casey from TAC. Remember, the class below yours? Hope all is well with you. I like your blog.

  2. PatrickH said,

    December 5, 2009 at 5:15 am

    Please bear with what will seem a stupid question (I remain a fascinated but struggling Thomistic newbie): but given that God is considered to be all-powerful, why is He never referred to by Thomists as pure potency, but always as pure act? While it is true that God is impassible, isn’t pure potency, protomatter, matter-as-such, also unchanging? If form actualizes it, it becomes determined and therefore no longer protomatter, which continues in its ineffable way to be pure potency, which is to say pure power, which is to say it can be anything possible, which is to say it is pure creative possibility. Or is it?

    Why isn’t it okay to think of God this way? Or is it?

    I appreciate you might not have time to answer my question, but is this question considered (and answered) somewhere to which you could refer me?

  3. December 5, 2009 at 7:30 am


    Good to hear from you. I’m that guy.


    While never calling him “pure potency”, we do call God “omnipotent”. that is, he is full of “potentia”. We don’t say he is “pure” potency because “pure” means “unmixed”, and our notion of potency is never unmixed. When we apply the term to God, we must deliberately and consciously purge out the mixed notion we have of it, and keep only the part of the notion that speaks to a perfection.

    The ideas of act and potency are exactly equivalent to perfection and the perfected (which latter is therefore, in itself, imperfect). The first sense of “power” is a mixed case: it is the perfection of one thing and is perfected by another, so it is in one sense act and in another potency. St. Thomas notes that we first call it potency because it is prior to, and underlying of, the fullest act: operation. So how are we to understand this “prior to” and “underlying”? In one sense, potentia underlies as imperfect, for it is perfected by operation; in another sense, potentia is more perfect than operation, for it causes it. Nevertheless, since we know material things best, our notion of “underlying” is always weighted towards matter, and so “potency” is inevitably pulled towards meaning what underlies as imperfect. One good reason not to call God “pure potency” is because the word is weighted towards meaning imperfection, even though the first thing we call “potency” (that is, the power to make) is most of all a perfection. And so while we can recognize that potency is said of God according to the first sense of the term- according to his power to make and create- the weight or pull of the term pulls towards imperfection, and so we avoid saying it of God.

    As for your remarks about first matter: while there are helpful likenesses that can be drawn between God and first matter, matter is always a way of speaking of imperfection, and the first matter of the most imperfect. Matter is a sort of fundament for all things, but only in a purely dependent way. In fact “pure matter” is simply a synonym of “pure dependence” or “pure imperfection”. God is utterly independent, existing in himself; pure matter is utterly dependent, existing in another. Everything else (like us) is somewhere between these extremes, but all of us nearer to God than first matter.

  4. December 5, 2009 at 8:45 am

    “Good to hear from you. I’m that guy.”

    Thanks. But are you “that guy”, for you regularly refer to the “senses” of words? You seem to be pointing out distinctions I hardly hear from my professors – and it’s much appreciated, by the way.

  5. December 5, 2009 at 8:57 am


    “but given that God is considered to be all-powerful, why is He never referred to by Thomists as pure potency”

    If I may venture an opinion (and please correct me, James, if I am wrong)…God is called “pure act” because both senses of the word, as form and as operation, can be attributed to God, while only one sense of potency -active potency (potentia active)- can be attributed to God. Thus it is not false to call God “pure potency” in terms of the potentia activa, but one would always have to insert the caveat that one is not referring to “passive potency” (potentia passiva). In point of fact, St. Thomas says -and does so in the De Potentia cited by James in this very article- that it is “most fitting” to call God potency -active potency.

    Forgive me if you were looking for more. I, myself, can only claim to be an aspirant. I’d be interested in hearing your thoughts.

  6. PatrickH said,

    December 5, 2009 at 9:40 am

    Thanks both. You have indeed answered my question. The key confusion, it seems to me, was my not remembering the distinction between first and second power. Clearly, passivity or dependence or perfectibility cannot be attributed to God, and these are the essence of first matter.

    God can make anything, but he can’t be made into anything, because he can’t be made at all. Matter can be made into anything, but it cannot make anything, because it cannot make at all.

    I partly asked the question because I’ve read in Frithjof Schuon, a proponent of the traditio perennis, that God can be understood as having two poles (this from our perspective only): one Absolute, the other Infinite, with the latter being identified as All-Possibility. If I understand both of you correctly, this would be incorrect if All-Possibility refers not to God’s omnipotence, but rather to matter’s infinite “malleability”, so to speak. There isn’t a Mother (matter) God in the sense of pure potential I was talking about above.

    If you don’t mind another question: how is first matter distinguished from simple nothingness? Is it the nihilo out of which God made creation?

  7. December 5, 2009 at 12:01 pm

    Your question, put positively, is “how does prime matter exist?”

    Start with the word “existence” which is said of certain things. Unambiguously, it is said of yourself, trees, fish, trees, stars, etc. It might expand a bit to include artifacts too- though not unambiguously. What about, say, “running” or “flesh tone”? Those exist too, I suppose, but you would want to put some sort of qualification on it, like “they exist, but dependently on another, and not primarily”. Still, if you limit yourself to what you mean first by “existence”, it dosn’t include orange or walking.

    Some people say that “whatever is not nothing exists, so I can have one meaning that applies to me, cars, the color yellow, running, etc.” This is, it seems to me, a ridiculous way of proceeding. We understand “nothing” or “non-being” by a negation of being. To try to turn around an define “being” by “non-being” is silly. If I don’t know what “shaud” means, it doesn’t help much to say “it is that which is other than non-shaud, and set apart from it”- but this is exactly what we do when we say that being is whatever is set apart from non-being or nothing.

    On this first meaning of “exists”, prime matter doesn’t exist. Neither, of course, does substantial form, last Tuesday, orange, running, a Euclidean sphere, the equation 2+2= 4, or God. But the sort of things that we say exist are bound up with these different things. What we say “exists” is bound up with another in various ways: sometimes by causing them, other times by being caused, sometimes by supporting them, other times by modeling them. The existent world causes and models the ens rationis or “mind dependent” world, and so it is distinct from the world of, say the plot of “Crime and Punishment” or the Euclidean sphere, and yet causes it. So we can extend the meaning of “exists” to this sphere so far as we see it as flowing from what we say is existent. In a similar way, we can see “accidents” as existent.

    Your question about prime matter is really a question of how it realted to the existent. I would say it relates as cause and principle. It is not a thing or existent, but more the principle of the existent. So far as it makes sense to extend the world “exists” to include what are first known as “prior-to-existence” things, then we can expand the word.

    So the first answer to your question is that prime matter dos not exist. This seems simply obvious. But if we pull out some qualifications and study the relations of things to the existent world, we can carve out a place for it as “principle of the existent”

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