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Monday, March 2, 2015


Commentary on actus essendi

Text no. 9

For a more extensive analysis of text no. 9 than what appears in this post, see my Actus essendi and the Habit of the First Principle in Thomas Aquinas (New York: Einsiedler Press, 2019), 124-132.



Commentary on 

Quodlibet IX, question 4, article 1, corpus 


In Quodlibet IX, question 4, article 1, corpus, Aquinas uses the expression actus essendi once. The matter being addressed in the article is whether or not angels are composed of matter and form. 

Two interrelated arguments are provided in support of the expected negative answer: (a) angels are intellectual beings; and (b) angels are incorporeal beings. I shall bypass discussion of these two arguments here.

Then Aquinas explains that angels, while not having composition of matter and form, can be said to possess composition of act and potency. Aquinas argues that the angel’s essence relates to the angel’s actus essendi as potency to act. Here is Aquinas in his own words:

Sed quia substancia angeli non est suum esse, hoc enim soli Deo competit cui esse debetur ex seipso et non ab alio, invenimus in angelo et substantiam sive quidditatem eius, quae subsistit, et esse eius, quo subsistit, quo scilicet actu essendi dicitur esse, sicut actu currendi dicimur currere. Et sic dicimus angelum esse compositum ex quo est et quod est, vel, secundum verbum Boetii, ex esse et quod est. Et quia ipsa substantia angeli in se considerata est in potencia ad esse, cum habeat esse ab alio, et ipsum esse est actus eius; ideo est in eo compositio actus et potencie. Et sic posset concedi in eo materia et forma, si omnis actus debeat dici forma et omnis potencia materia. Set non competit in proposito, quia esse non est actus qui sit pars essencie, sicut forma, ipsa etiam quiditas angeli vel substancia est per se subsistens, quod materiae non competit(Quodlibet IX, question 4, article 1, corpus, Rome: Leonine edition, 1996, vol. 25, fasc. 2/1, p. 102 Column B, lines 115-124 and p. 103 column A, lines 125-132).

John F. Wippel cites this passage as example of an argument for the distinction and composition of essence and actus essendi in creatures. And according to Wippel, this argument belongs to the group of arguments which require as one of their working principles prior knowledge of God’s existence. In Wippel’s terminology, the argument is an example of a “God-to-creatures” kind of argumentation in favor of the real distinction. (See J. F. Wippel, The Metaphysical Thought of Thomas Aquinas [Washington, D.C.: Catholic University of America Press, 2000], 588-589.)

Wippel writes: “Another brief version of ‘God-to-creatures’ argumentation appears in Thomas’s only slightly later Quodlibet IX of Christmas 1257. There in q. 4, a.1 he was asked whether an angel is composed of matter and form. After arguing at some length against this position, Thomas wants to show that there is act-potency composition in angels nonetheless. He counters that because the substance of an angel is not identical with its act of being, something which is true of God alone to whom esse belongs of himself and not from something else, we find in an angel both a substance or quiddity, which subsists, and its act of being, by means of which it subsists or exists. Because the substance of an angel viewed in itself is in potency to the act of being it receives from something else, there is a composition of potency and act therein.”

Then Wippel continues: “Most interesting for our immediate purpose is Thomas’s briefly stated reason for holding that the substance of an angel is not identical with its act of being. This, he says, is true of God alone to whom esse belongs of himself and is not derived from something else. In other words, he reasons from the fact that God’s act of being is uncaused to the conclusion that in him essence and act of being are identical, and from this to the contrast with all other things. In all of them essence and act of being differ and are therefore composed. Presumably this is because, unlike God, they receive their esse from something else and therefore enter into composition with it. Thomas does not explicitly state this, however. It could be that he simply protects the divine simplicity by immediately concluding to the necessarily composed character of things other than God. In any event, the argument accepts God’s existence as granted along with the fact that his act of being is uncaused and is, therefore, identical with his essence.”

The footnote to this paragraph reads as follows: “Because Thomas introduces this argumentation almost as an obiter dictum [as something stated incidentally in the discussion] to support distinction of essence and esse in angels and his refutation of matter-form composition in them, we should not expect him to develop it fully for its own sake here. Brief though it is, it does move from identity of essence and esse in God alone to their otherness or distinction in everything else.”

It should be noted also that the text contains a brief explanation of how the expression actus essendi is to be understood. Aquinas explicitly connects the expression actus essendi with the axiom from Boethius ‘diversum est esse et quod est,’ and he also indicates explicitly that in this context actus essendi and esse signify in the way actus currendi and currere signify. (See Entry 391: “Commentary on Actus Essendi – Text no. 7;” and Entry 387: “Commentary on Actus Essendi – Text no. 3.”)