Commentary on actus essendiText no. 6

For a more extensive analysis of text no. 6 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), 110-112.

Commentary on 
De veritate, question 1, article 1, ad 1 

In De veritate, question 1, article 1, Aquinas explicitly uses the expression actus essendi five times: once in the corpus, once in the response to the first objection, and three times in the response to the third argument in the sed contra. In this post I shall comment on the context surrounding the text presented in the response to the first objection.

After having established in the corpus that the term verum expresses a modus essendi that the term ens does not express (see also De veritate, question 1, article 10, ad 2), Aquinas explains in his answer to the first objection that from the definition of Saint Augustine—“verum est id quod est”—one cannot conclude that “verum means exactly the same as ens.” In other words, the statement “verum est id quod est” and the statement “ens est id quod est” are not equivalent statements.

In the body of the article, Aquinas had already established that the res significata of the term ens is the metaphysical principle of actus essendi instantiated in the self-subisting things of nature. Now the reasoning presented in the present objection allows him to explain that this primary meaning of ens extends to the verb “est.”

In the statement “ens est id quod est,” the “est” of the “id quod est” has indeed the actus essendi as its primary meaning. But in the statement “verum est id quod est,” the “est” of the “id quod est” has a wider scope, since this “est” can by extension refer to the qualified esse of the second operation of the intellect.

The res significata which functions as the direct object of a particular act of intellection quite often is not a self-subsisting thing. However, the human intellect always attributes some sort of esse to any object of intellection and the intellect seeks to make this attribution correctly, that is to say, the intellect attributes esse in conformity with the reality of the apprehended object. Accidents, for example, are not subsisting entities, but when accidents are grasped as the res significata of an act of intellection, accidents are credited with esse in a qualified sense.

Aquinas understands that for the term “ens” in its meaning of “id quod est” there are two elements, the “quod” and the “est.” But Aquinas emphasizes that the composition thus signified does not possess the elements required for it to be a “composition which is susceptible of truth and falsity.” (See Jan A. Aertsen Medieval Philosophy and the Transcendentals: The Case of Thomas Aquinas [Leiden: E. J. Brill, 1996], 180.)

Accordingly, in his answer to the present objection Aquinas explains that in the definition of verum given by Saint Augustine, the “est” of the “id quod est” does not refer to the unqualified esse which he calls actus essendi; in the definition of verum given by Saint Augustine, the “est” of the “id quod est” refers to a qualified esse to which the connotation of true and false applies (ut sit sensus: verum est “id quod est,” id est cum dicitur esse de aliquo quod est).

In explaining his understanding both of the res significata and of the ratio significata of the verb esse as used in the third person of the present indicative tense (the Latin “est”), Aquinas clearly demarcates two kinds of esse: (1) unqualified esse which is the actus essendi instantiated by the self-subisting things of nature, and (2) qualified esse which is the esse of anything that in any way whatsoever can be said to be. 

The human intellect directs its attention to the res significata through an intellectual conception, and the primary meaning of the verb “est” is indeed the actus essendi of a subsisting thing. 

But by extension the meaning of “est” can accommodate also the intellectual conception of any other perfection that inheres in a subsisting thing. Even the intellectual conception of lack of a perfection or figments of the imagination can by extension be accommodated under the meaning of “est.”

Here is the objection and the response in the words of Aquinas:

Objection: Augustinus in lib. Solil. (cap v) dicit, quod verum est id quod est. Sed id quod est, nihil est nisi ens. Ergo verum significat omnino idem quod ens.

Answer: Ad primum ergo dicendum quod definitio illa Augustini datur de veritate secundum quod habet fundamentum in re, et non secundum id quod ratio veri completur in adaequatione rei ad intellectum. Vel dicendum, quod cum dicitur verum est “id quod est,” li “est” non accipitur ibi secundum quod significat actum essendi, sed secundum quod est nota intellectus componentis, prout scilicet affirmationem propositionis significat, ut sit sensus: verum est “id quod est,” id est cum dicitur esse de aliquo quod est.

Regarding the way Aquinas interprets the definition of verum given by Saint Augustine, John F. Wippel writes:

“[I]n replying to the first objection, Thomas suggests, as he had already done in the corpus, that Augustine’s first-mentioned definition of truth as ‘that which is’ might be taken as referring only to truth’s foundation in reality, not to its nature as perfected through an adequation of a thing to an intellect. Or it might be reinterpreted much as Thomas had previously suggested in his Commentary on I Sentences so as to refer not to a thing’s act of being (actus essendi) but only to the being produced by the intellect when it judges (composes and divides). In other words, it might be shifted from truth of being to truth of the intellect” (J. F. Wippel, Metaphysical Themes in Thomas Aquinas II [Washington, D.C.: Catholic University of America Press, 2007], 80).

In the footnote to this paragraph Wippel quotes the Leonine edition (Leon. 22.1.6.), and then adds: “Note from the second solution: ‘Vel dicendum quod cum dicitur verum est id quod est, li est non accipitur ibi secundum quod significat actum essendi sed secundum quod est nota intellectus componentis, prout scilicet affirmationem propositionis significat … ut sic in idem redeat definitio Augustini cum definitione Philosophi supra inducta’ (lines 205-213). Note Thomas’s explicit reference to est as not signifying the act of being on this reading. This would suggest that in referring to truth as grounded in a thing’s esse in In I Sent., d. 19, q. 5, a. 1, Thomas may also have in mind a thing’s intrinsic act of being rather than its mere facticity (nn. 6-7 above). Cf. my The Metaphysical thought, pp. 31-33.)”

J. A. Aertsen for his part points out that the central place that Aquinas gives to the definition of truth as adaequatio in his arrangement of the definitions of truth in the corpus of the article implies a criticism to the definition of Augustine. 

Aertsen writes: “Thomas arranges the various definitions of truth from the tradition on the basis of the three elements contained in the conformity formula: the thing, the intellect, and the relation between these two” (J. A. Aertsen, Medieval Philosophy and the Transcendentals: The Case of Thomas Aquinas [Leiden: E. J. Brill, 1996], 253).

The adaequatio relation, Aertsen explains, is a relation between the intellect and the extra-mental thing, which means that the intellect itself pertains to the essence of truth. Thus, Aertsen stresses that Augustine’s definition is too limited and is imperfect because it concerns only the foundation of truth. 

Aertsen then continues: “Thomas criticizes Augustine’s definition (‘that which is’) that it does not express the complete concept of truth, which consists in the conformity of thing and intellect. He also proposes an alternative interpretation that understands Augustine’s definition in an Aristotelian sense. When truth is defined as ‘that which is,’ this ‘is’ must be taken as signifying the affirmation of a proposition; its meaning then is that there is truth when that-which-is, is said to be. Augustine’s definition is transformed into the sense of intra-mental being [being as verbal copula], which the Philosopher called ‘that which is true’” (Aertsen, Medieval Philosophy and the Transcendentals, 256).

The conclusion of Aertsen is that “Augustine’s definition does not express fully the essence of truth; it is in relation to the intellect that a thing is called true according to what it is and false according to what it is not.” In support of this Aertsen refers to De veritate, question 1, article 10, ad 1: “Ad primum ergo dicendum, quod ista definitio, verum est id quod est, non perfecte exprimit rationem veritatis, sed quasi materialiter tantum, nisi secundum quod li esse significat affirmationem propositionis, ut scilicet dicatur id esse verum quod sic esse dicitur vel intelligitur ut in rebus est; et sic etiam falsum dicatur quod non est, id est quod non est ut dicitur vel intelligitur; et hoc in rebus inveniri potest.” (See Aertsen, Medieval Philosophy and the Transcendentals, 279.)

There is no room for doubt that in De veritate, question 1, article 1, ad 1, the res significata of the expression “actus essendi” is the intrinsic metaphysical principle which accounts for the being real of an extramental subsisting thing.

Commentary on actus essendiText no. 5

For a more extensive analysis of text no. 5 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), 105-108.

Commentary on 
De veritate, question 1, article 1, corpus 

In De veritate, question 1, article 1, Aquinas explicitly uses the expression actus essendi five times: once in the corpus, once in the response to the first objection, and three times in the response to the third argument in the sed contra. In this post I shall comment on the context surrounding the text presented in the corpus.

The first article of De veritate deals with the question “What is truth?” but the article contains what has been called “the most systematic derivation” of the transcendental notions written in the thirteenth century. 

(See Jan A. Aertsen, “Thomas Aquinas: A First Model,” in Medieval Philosophy as Transcendental thought: From Philip the Chancellor (ca. 1225) to Francisco Suárez [Leiden: E. J. Brill, 2012], 211. For a more thorough analysis of the text of De veritate, question 1, article 1, see also J. A. Aertsen, Medieval Philosophy and the Transcendentals: The Case of Thomas Aquinas [Leiden: E. J. Brill, 1996], chapter 2.)

The expression actus essendi appears in the first part of the article as Aquinas explains that the inquiry into what something is, requires antecedent knowledge. In conducting such inquiry, Aquinas affirms, previous knowledge should not be extended into an infinite regress for that would render the formation of concepts impossible. 

Thus the beginning of human thought, Aquinas postulates, is a primary notion which the human intellect conceives immediately. This is the notion of ens. No other previously known notion is needed for the human intellect to conceive ens, for ens is that which the intellect conceives first and quasi notissimum from the information supplied by sensible experience. 

Ens is not only the first notion in concept formation, ens is also the first among the other primary notions for the notion of ens is included in the understanding of any other notion.

Having established the absolute priority of the notion of ens, Aquinas proceeds to explain that all intellectual activity consists in adding something to the always present primary intellectual conception of ens. 

This addition, however, is unique in the sense that anything that in any way whatsoever is proposed to be added to ens is already ens, and, so, nothing can really be added to ens in the way species are added to a genus or accidents to a subject. 

The species of man, for example, adds to animal the connotation of rational which the genus animal does not possess. But nothing can be added in this way to ens, for under the notion of ens, all animals are ens, all men are ens, and all things are ens. This is the reason why ens is not a genus. 

Addition is then said to be applicable to the notion of ens when what is added expresses a modus entis that the word ens does not express. And here Aquinas distinguishes between (a) added expressions that refer to a special modus entis and (b) added expressions that refer to a general modus entis.

In the special modus entis Aquinas places the categories of substance and accidents, none of which add to ens anything that can be considered an addition of a species added to a genus. What the categories of substance and accidents add to the notion of ens is that they express a special modus essendi, like ens per se in the case of substance and ens in alio in the case of accidents.

In the general modus entis Aquinas further distinguishes between (a) added expressions that refer to ens considered in itself and (b) added expressions that refer to ens in what regards the relation of one ens to another. 

The first of these two sub-groups lists the added expressions of res and unum. The second sub-group includes the added expressions of aliquid, bonum, and verum.

It is in his explanation of how the word res expresses something that the notion of ens does not express that Aquinas introduces the term actus essendi in the present article. In every ens, he says, one finds an essence as the recipient of esse. But essence is that from which the name res is imposed. Thus, following Avicenna Aquinas contends that the difference between ens and res is this, that the name ens is taken from the actus essendi, while the name res expresses the essence or quiddity of the thing.

Thus Aquinas writes:

“Sicut in demonstrabilibus oportet fieri reductionem in aliqua principia per se intellectui nota, ita investigando quid est unumquodque; alias utrobique in infinitum iretur, et sic periret omnino scientia et cognitio rerum. Illud autem quod primo intellectus concipit quasi notissimum, et in quod conceptiones omnes resolvit, est ens, ut Avicenna dicit in principio suae Metaphysicae. Unde oportet quod omnes aliae conceptiones intellectus accipiantur ex additione ad ens. Sed enti non possunt addi aliqua quasi extranea per modum quo differentia additur generi, vel accidens subiecto, quia quaelibet natura est essentialiter ens; unde probat etiam Philosophus in III Metaphys., quod ens non potest esse genus, sed secundum hoc aliqua dicuntur addere super ens, in quantum exprimunt modum ipsius entis qui nomine entis non exprimitur. Quod dupliciter contingit: uno modo ut modus expressus sit aliquis specialis modus entis. Sunt enim diversi gradus entitatis, secundum quos accipiuntur diversi modi essendi, et iuxta hos modos accipiuntur diversa rerum genera. Substantia enim non addit super ens aliquam differentiam, quae designet aliquam naturam superadditam enti, sed nomine substantiae exprimitur specialis quidam modus essendi, scilicet per se ens; et ita est in aliis generibus. Alio modo ita quod modus expressus sit modus generalis consequens omne ens; et hic modus dupliciter accipi potest: uno modo secundum quod consequitur unumquodque ens in se; alio modo secundum quod consequitur unum ens in ordine ad aliud. Si primo modo, hoc est dupliciter quia vel exprimitur in ente aliquid affirmative vel negative. Non autem invenitur aliquid affirmative dictum absolute quod possit accipi in omni ente, nisi essentia eius, secundum quam esse dicitur; et sic imponitur hoc nomen res, quod in hoc differt ab ente, secundum Avicennam in principio Metaphys., quod ens sumitur ab actu essendi, sed nomen rei exprimit quidditatem vel essentiam entis” (De veritate, question 1, article 1, corpus).

For our purposes here it is important to observe that in this text Aquinas is establishing a connection between the beginning of knowledge and the ratio significata of the term ens which is the notion or intellectual conception of the actus essendi: (a) Illud in quod intellectus conceptiones omnes resolvit est ens, and (b) ens sumitur ab actu essendi.

Commentary on actus essendiText no. 4

For a more extensive analysis of text no. 4 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), 93-97.

Commentary on 
In III Sententiarum, distinction 11, question 1, article 2, ad 2 

In this article Aquinas asks whether Christ can be said to be creatura. In the answer to the question Aquinas structures an argument based on the primary signification of the analogous term esse.

With the expression simpliciter et per se (and its opposite secundum quid et per accidens) Aquinas emphasizes that the primary meaning of the term esse refers to the esse that belongs to the subsisting suppositum. 

Aquinas explains that esse can be said to belong to the form—forma—because the subsisting suppositum is essentially composed of matter and form; and for the same reason, esse can be said to belong to matter. In the material world, matter and form are the essential principles of a subsisting suppositum, that is, the composite. 

Similarly, esse can be said to belong to accidents because accidents inhere in the subsisting suppositum. 

Thus when esse is said of a form, or when esse is said of matter, or when esse is said of accidents, esse is said in a qualified sense. Only of the subsisting suppositum is esse affirmed simpliciter et per se. 

It is only because of the relation of matter, form, and accidents to the esse of the subsisting suppositum that matter, form, and accidents can be said to possess esse in a qualified sense.

The esse of the subsisting suppositum is said to come into existence per modum creationis. But the esse of the quiddity (which is the material nature composed of matter and form) and the esse of accidents, are said to come into existence per modum informationis. 

According to Aquinas, Aristotle postulated that the world always existed with a constant uninterrupted flow of generation and corruption of things, and that it was through such beginningless and endless chain of perishable pre-existing materials that Aristotle understood how things come into existence in the visible world per modum informationis. 

While preserving some elements of such conception of the world, Aquinas understood things differently, since for Aquinas a subsisting suppositum ultimately comes into existence per modum creationis.

Now in the case of human beings, the simpliciter et per se meaning of esse refers to the esse of the person. 

Thus, the affirmation Christus est signifies the personal esse of Christ, not the esse of His nature, nor the esse of His accidents, and certainly not the esse of any of the essential principles of His Most Holy Humanity, all of which can be said to possess esse only in a qualified sense.

The union of the divine nature and the human nature takes place in only one suppositum which is the divine suppositum, the only suppositum that Christ has. In Christ there is no human suppositum. In Christ there is no human person. 

Christ is only one person, the Second Person of the Most Blessed Trinity, the person in whom the hypostatic union of two natures, the human and the divine, takes place.

Therefore, Christ cannot be said to be creatura. The esse of Christ is only one, that is, the divine, uncreated esse. 

Christ is not creatura, but just as esse can be said in a qualified sense of matter, form, and accidents, some things that belong to Christ can be said to be created.

Thus Aquinas writes:

“Respondeo dicendum, quod creatio proprie respicit esse rei: unde dicitur in lib. De causis, quod esse est per creationem, alia vero per informationem. Esse autem simpliciter et per se est suppositi subsistentis; alia vero dicuntur esse, inquantum suppositum in eis subsistit, vel essentialiter, sicut materia et forma, et sic natura ipsa dicitur esse; vel accidentaliter, sicut accidentia dicuntur esse. Esse ergo dictum simpliciter de supposito significat esse personale ipsius; esse vero, secundum quod convenit parti vel accidenti, non dicitur simpliciter de supposito, sed suppositum dicitur esse in eo; unde cum dico: ‘Christus est,’ significatur esse ipsius, non autem esse ipsius naturae, vel accidentis, vel partis. Cum autem fiat unio naturarum in esse suppositi secundum secundam opinionem, esse, secundum quod Christus simpliciter esse dicitur, est esse increatum; unde non potest dici creatura, non tantum ad evitandum errorem Arii, ut quidam dicunt, sed etiam ad vitandum falsitatem. Potest tamen dici, quod aliquid creatum est in Christo, scilicet humana natura; quia esse quamvis sit unum, tamen respectum habet ad naturam et ad partes ejus, secundum quas humana natura dicitur esse in Christo, vel partes aut accidentia ejus, ut supra, dist. 6, dictum est. Unde sicut esse aliquo modo ad naturam pertinet, et ad partes et accidentia ejus, ita et creatio” (In III Sententiarum, distinction 11, question 1, article 2, corpus).

With this background Aquinas proceeds to respond to the following objection: When there are lower categories contained in a higher category, things that are contained in a lower category are also contained in the higher one. Now the category of man—homo, and several other categories, belong to the wider category of creatura. Therefore, if we affirm that Christ is man—homo, as we do when we confess our faith, we should also affirm that Christ is creatura.

To this objection Aquinas responds with a flat negation of the assumption that creatura is a wider category than the category of man—homo. One reason is that what comes into existence per modum creationis is the esse of the subsisting suppositum, not its quiddity. Now the esse of the subsisting supposita do not generate a category or genus as their quidditas does: what is common to things contained in a category or genus is their quiddity, not their esse. 

Or better explained, the intellectual conception expressed by the term creatura cannot be said to be superior to the intellectual conception expressed by the term man—homo—on account of the way these conceptions relate to the quiddity of man. 

The activity of creation, Aquinas affirms, does not relate to quiddity except through the actus essendi which is the first, of created things—primus terminus creationis. Therefore, on the side of the quiddity, Christ may be said to have a created humanity. But on the side of the actus essendi, the person of Christ possesses the uncreated actus essendi of God. Therefore the person of Christ cannot be said to come into existence per modum creationis.

Here is the objection as Aquinas wrote it, and the response in his own words:

“Praeterea, de quocumque praedicatur inferius, et superius. Sed creatura est superius ad hominem. Ergo cum homo praedicetur de Christo, creatura de ipso praedicabitur” (In III Sententiarum, distinction 11, question 1, article 2, argument 2).

“Ad secundum dicendum, quod creatura non est superius ad hominem: quia creatio magis respicit esse quam naturam. Esse autem non est genus, nec inducitur in significatione alicujus generis, ut dicit Avicenna, cum ea quae sunt in uno genere, non conveniant in uno esse, sed in natura communi. Vel dicendum, quod creatura non est superius ad hominem, significans quid est homo: quia creatio non respicit naturam vel essentiam, nisi mediante actu essendi; qui est primus terminus creationis. Humana autem natura in Christo non habet aliud esse perfectum, quod est esse hypostasis, quam esse divinae personae; et ideo, simpliciter loquendo, creatura dici non potest: quia intelligeretur quod esse perfectum hypostasis Christi per creationem esset acquisitum” (In III Sententiarum, distinction 11, question 1, article 2, ad 2).

This text is important because it explicitly manifests how Aquinas conceived the connection between the notion of creation and the notion of actus essendi: (1) “Creatio proprie respicit esse rei,” and (2) Actus essendi “est primus terminus creationis.”

For Aquinas esse, in its meaning of actus essendi, belongs properly to that which has esse, that is, to what subsists in its own esse. Thus, properly speaking what comes into existence per modum creationis is the subisting things of nature. Accordingly, in the Summa theologiae Aquinas writes: “Proprie vero creata sunt subsistentia” (part I, question 45, article 4, corpus.)

There is no room for doubt that in this text the res significata of the term actus essendi is the metaphysical principle of actus essendi as instantiated in a subsisting suppositum. 

Commentary on actus essendiText no. 3

For a more extensive analysis of text no. 3 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), 83-91.

Commentary on 
In I Sententiarum, distinction 8, question 5, article 2, corpus 

The article addresses the issue of the kind of composition that can be attributed to the human soul. Given that a human being is composed of soul and body, Aquinas first asks whether or not the human soul itself can be said to be composed of matter and form. The answer is given with the argument that forms need to be separated from matter to be intelligible in act. From this it follows that substances which are by nature intelligible in act are not material. And since the human soul is this kind of substance, the human soul is not composed of matter and form.

Secondly Aquinas examines the opinion of others who say that the human soul is composed of “quo est” and “quod est.” Here Aquinas first establishes that quod est does not refer to primary matter. Quod est refers to entities that possess esse properly, and these are only the subsisting supposita. As a quod est, a subsisting suppositum is said to be the possessor of esse, that is to say, a suppositum is an habens esse.

Now, in the material world a subsisting suppositum is composed of matter and form. Therefore, primary matter itself is not an habens esse; the composite is the habens esse. Thus, in all entities in which one finds the composition of primary matter and form, one also finds another composition, the composition of quo est and quod est. With this background, Aquinas then explains that in things composed of primary matter and form, the term quo est can take three different meanings.

It is within this context that Aquinas introduces the term actus essendi as the second meaning of the expression quo est:

(a) Potest enim dici quo est ipsa forma partis, quae dat esse materiae.

(b) Potest dici quo est ipse actus essendi, scilicet esse, sicut quo curritur, est actus currendi.

(c) Potest etiam dici quo est ipsa natura quae relinquitur ex conjunctione formae cum materia, ut humanitas; praecipue secundum ponentes quod forma, quae est totum, quae dicitur quidditas, non est forma partis, de quibus est Avicenna.

Here is the full text:

“Alii dicunt, quod anima est composita ex quo est et quod est. Differt autem quod est a materia; quia quod est, dicit ipsum suppositum habens esse; materia autem non habet esse, sed compositum ex materia et forma; unde materia non est quod est, sed compositum. Unde in omnibus illis in quibus est compositio ex materia et forma, est etiam compositio ex quo est et quod est. In compositis autem ex materia et forma quo est potest dici tripliciter. Potest enim dici quo est ipsa forma partis, quae dat esse materiae. Potest etiam dici quo est ipse actus essendi, scilicet esse, sicut quo curritur, est actus currendi. Potest etiam dici quo est ipsa natura quae relinquitur ex conjunctione formae cum materia, ut humanitas; praecipue secundum ponentes quod forma, quae est totum, quae dicitur quidditas, non est forma partis, de quibus est Avicenna. Cum autem de ratione quidditatis, vel essentiae, non sit quod sit composita vel compositum; consequens poterit inveniri et intelligi aliqua quidditas simplex, non consequens compositionem formae et materiae. Si autem inveniamus aliquam quidditatem quae non sit composita ex materia et forma, illa quidditas aut est esse suum, aut non. Si illa quidditas sit esse suum, sic erit essentia ipsius Dei, quae est suum esse, et erit omnino simplex. Si vero non sit ipsum esse, oportet quod habeat esse acquisitum ab alio, sicut est omnis quidditas creata. Et quia haec quidditas posita est non subsistere in materia, non acquireretur sibi esse in altero, sicut quidditatibus compositis, immo acquiretur sibi esse in se; et ita ipsa quidditas erit hoc quod est, et ipsum esse suum erit quo est. Et quia omne quod non habet aliquid a se, est possibile respectu illius; hujusmodi quidditas cum habeat esse ab alio, erit possibilis respectu illius esse, et respectu ejus a quo esse habet, in quo nulla cadit potentia; et ita in tali quidditate invenietur potentia et actus, secundum quod ipsa quidditas est possibilis, et esse suum est actus ejus. Et hoc modo intelligo in Angelis compositionem potentiae et actus, et de quo est et quod est, et similiter in anima. Unde Angelus vel anima potest dici quidditas vel natura vel forma simplex, inquantum eorum quidditas non componitur ex diversis; tamen advenit sibi compositio horum duorum, scilicet quidditatis et esse” (In I Sententiarum, distinction 8, question 5, article 2, corpus).

Aquinas thus explains in the present text that the term quidditas does not respond to a ratio that restricts the meaning  of “quidditas” to what is composed and, for this reason, it is possible to conceive intellectually—and also to find in reality—a quiddity that is simple and devoid of the composition of matter and form. Such simple quiddity would either be its own esse as is the case of God who is simple absolutely, i.e., simple without qualification; or it would be a quiddity that is simple in the qualified sense of an habens esse ab alio. The latter is the case of angels and the human soul. In angels and souls there is no composition of matter and form but only the composition of actus essendi (quo est) and simple quiddity (quod est).

It is with reference to the other two meanings of quo est—the quo est as forma partis and the quo est as forma totius—that Cornelio Fabro highlights the uniqueness of Aquinas’s actus essendi. Thus Fabro writes, “esse in senso proprio è soltanto l’actus essendi, che dà il sussistere alla sostanza,” which is translated as follows: “that by which the substance subsists is the actus essendi, and the term esse properly speaking means the actus essendi.” (1) Fabro affirms that the analysis of the expression quo est delivered in the present text shows how Aquinas transformed the Aristotelian terminology by introducing the notion of actus essendi.

A number of observations can be made concerning the meaning of the term actus essendi. 

In the present text the term actus essendi appears with a well defined meaning. It is presented as the second meaning of the expression quo est and as one of the explicit meanings of the verb esse. As quo est the actus essendi signifies in abstracto the measure of reality that is instantiated in a quod est. And as one of the explicit meanings of the verb esse, Aquinas explains that actus essendi or esse is to quo est what actus currendi or currere is to quo curritur.

The res significata of currere is the action of running. Thus the expressions currere and actus currendi signify per modum actionis. Similarly the res significata of the verb esse in this context is the metaphysical principle of actus essendi, which the expressions esse and actus essendi signify per modum actionis. Regarding this Jan A. Aertsen has commented that verbs in general signify something after the manner of an action or passion, and that for this reason the verb esse—which he translates as “to be”—must also bring to expression some activity. “But Thomas sees a fundamental difference,” Aertsen continues, “between ‘to be’ and the other verbs. Other verbs, like ‘to run,’ signify accidental actions. Esse, however, is not a secondary act, but the primary” (J. A. Aertsen, Medieval Philosophy and the Transcendentals: The Case of Thomas Aquinas [Leiden: E. J. Brill, 1996], 190).

The present text also makes clear that the counterpart of the metaphysical principle of actus essendi is the substantial quidditas, not accidental quidditas.

Note

(1) Cornelio Fabro, Partecipazione e Causalita (Torino: Società Editrice Internazionale, 1960) 203, my translation. In explaining the other two meanings of the phrase quo est, Aquinas, however, explicitly attributes the doctrine to Avicenna. The forma totius relates to the forma partis as whole to part. The forma totius is the quiddity that results from the conjunction of substantial form and matter, understanding these as abstracted from the individual conditions. Thus, the terms homo and humanitas are two ways of designating the forma totius: homo signifies the quiddity per modum totius, and humanitas signifies the same quiddity per modum partis. The forma partis, on the other hand, is the human soul which is the substantial form or forma partis quae dat esse corpori. (For more on this see John F. Wippel, The Metaphysical Thought of Thomas Aquinas [Washington, D.C.: Catholic University of America Press, 2000] 201-202, and reference there in.)