The Ways to Wisdom
Aquinas Day By Day


Aquinas’s topic: logic of arguments: “said through itself,” mode 1


Aquinas’s text: Expositio libri Posteriorum , Bk. 1, lec. 10

The phrase “through itself (per se)” is a term of art Aristotle invented in order to deal with questions that Plato had attempted to answer by positing his theory of forms.  Br. Thomas here begins his commentary by looking at the phrase.  The reflexive “itself (se)” indicates that the phrase looks inside a thing to its inner essence or nature.  When limited to propositions describing a thing’s essence, there are only two possibilities:  either the predicate of the proposition sets out all or part of the essence of the subject, or the reverse is true, the subject setting out all or part of the essence of the predicate.  The first two “modes” of per se, then, clearly work together, and seem to have come from Aristotle’s reflection on a dialectical exercise he learned in Plato’s Academy—dividing concepts in order to generate definitions of the forms or essences of things.  Because the first two modes of per se are set out in terms of a thing’s definition, it is often accurate in English to translate these two modes of per se as “essentially.”  However, since Br. Thomas is addressing the meaning of all four modes of per se, the more literal translation “through itself” will be used here.

After he has determined about “said of all,” the Philosopher now determines about “through itself (per se).” On this topic he does three things. First, he shows the number of modes in which something is said “through itself (per se);  second, how the demonstrator uses these modes (73b16); and third, he summarizes (73b25).

Concerning the first point, one must know that the preposition “through (per)” designates a relation to a cause, although sometimes it also signifies a state, as when someone is said to be “by himself (per se)” when he is alone. When it designates a relation to a cause, sometimes the cause is formal, for example, when it is said that the body lives “through” the soul; and sometimes the relation is to a material cause, for example, when it is said that a body is colored “through” its surface, that is, because the surface is the proper subject of color.  It also designates a relation to an extrinsic cause, especially an efficient cause, for example, when it is said that water becomes hot “through” fire. Now just as the preposition “through (per)” designates a relation to a cause when something extrinsic is its cause, so likewise when the subject or something pertaining to the subject is the cause of that which is attributed to it, this is signified by the phrase “through itself (per se).”

Therefore, the first mode of something being said “through itself (per se)” (73a34) is when that which is attributed to something pertains to its form. And because a definition signifies the form and essence of a thing, the first mode of that which is “through itself (per se)” is when there is predicated of something a definition or something found in the definition. This is what he means when he says that the “through themselves” are whatever are in the “quiddity,” that is, in the definition expressing the “quiddity,” whether they are put in the nominative case or in one of the oblique cases. For example, in the definition of a “triangle” is put “line,” so that “line” is in “triangle” through itself (per se). Likewise, in the definition of “line” is put “point,” so that “point” is in “line” through itself (per se).  Now he adds the reason why these things are put in the definition when he says “the substance,” that is, the essence “of them,” that is, of triangle and line, “is from these things,” that is, from lines and points. However, this should not be understood to mean that a line is composed of points, but rather that a point is part of the very meaning of line, just as line is part of the very meaning of triangle. And he says this in order to exclude things that are parts of a thing’s matter but not of its species.  These are not put into its definition, as, for example, “semicircle” is not put into the definition of a circle, and “finger” is not put into the definition of a human, as it said in Metaphysics 7. And he adds that all those things that are found universally in the definition expressing quiddity are attributed to something through itself (per se).

Postquam determinavit philosophus de dici de omni, hic determinat de per se. Et circa hoc duo facit: primo, ostendit quot modis dicitur aliquid per se; secundo, ostendit qualiter his modis demonstrator utatur; ibi: quae ergo dicuntur et cetera.

Circa primum sciendum est quod haec praepositio per designat habitudinem causae; designat etiam interdum et situm, sicut cum dicitur aliquis esse per se, quando est solitarius. Causae autem habitudinem designat, aliquando quidem formalis; sicut cum dicitur quod corpus vivit per animam. Quandoque autem habitudinem causae materialis; sicut cum dicitur quod corpus est coloratum per superficiem: quia scilicet proprium subiectum coloris est superficies. Designat etiam habitudinem causae extrinsecae et praecipue efficientis; sicut cum dicitur quod aqua calescit per ignem. Sicut autem haec praepositio per designat habitudinem causae, quando aliquid extrinsecum est causa eius, quod attribuitur subiecto; ita quando subiectum vel aliquid eius est causa eius, quod attribuitur ei, et hoc significat per se.

Primus ergo modus dicendi per se est, quando id, quod attribuitur alicui, pertinet ad formam eius. Et quia definitio significat formam et essentiam rei, primus modus eius quod est per se est, quando praedicatur de aliquo definitio vel aliquid in definitione positum (et hoc est quod dicit quod per se sunt quaecunque insunt in eo, quod quid est, idest in definitione indicante quid est), sive ponatur in recto sive in obliquo. Sicut in definitione trianguli ponitur linea; unde linea per se inest triangulo: et similiter in definitione lineae ponitur punctum; unde punctum per se inest lineae. Rationem autem quare ista ponantur in definitione subiungit dicens: substantia, idest essentia, quam significat definitio ipsorum, idest trianguli et lineae, est ex his, idest ex linea et punctis. Quod non est intelligendum quod linea ex punctis componatur, sed quod punctum sit de ratione lineae, sicut linea de ratione trianguli. Et hoc dicit ad excludendum ea, quae sunt partes materiae et non speciei, quae non ponuntur in definitione, sicut semicirculus non ponitur in definitione circuli, nec digitus in definitione hominis, ut dicitur in VII metaphysicae. Et subiungit quod quaecumque universaliter insunt in ratione dicente quid est, per se attribuuntur alicui.

[Introductions and translations © R.E. Houser]

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