Thomas Aquinas, Summa Theologiae

Objection 1: It seems that God is not altogether simple. For whatever is from God must imitate Him. Thus from the first being are all beings; and from the first good is all good. But in the things which God has made, nothing is altogether simple. Therefore neither is God altogether simple.

Objection 2: Further, whatever is best must be attributed to God. But with us that which is composite is better than that which is simple; thus, chemical compounds are better than simple elements, and animals than the parts that compose them. Therefore it cannot be said that God is altogether simple.

On the contrary, Augustine says (De Trin. iv, 6,7): "God is truly and absolutely simple."

I answer that, The absolute simplicity of God may be shown in many ways. First, from the previous articles of this question. For there is neither composition of quantitative parts in God, since He is not a body; nor composition of matter and form; nor does His nature differ from His "suppositum"; nor His essence from His existence; neither is there in Him composition of genus and difference, nor of subject and accident. Therefore, it is clear that God is nowise composite, but is altogether simple. Secondly, because every composite is posterior to its component parts, and is dependent on them; but God is the first being, as shown above (Question 2, Article 3). Thirdly, because every composite has a cause, for things in themselves different cannot unite unless something causes them to unite. But God is uncaused, as shown above (Question 2, Article 3), since He is the first efficient cause. Fourthly, because in every composite there must be potentiality and actuality; but this does not apply to God; for either one of the parts actuates another, or at least all the parts are potential to the whole. Fifthly, because nothing composite can be predicated of any single one of its parts. And this is evident in a whole made up of dissimilar parts; for no part of a man is a man, nor any of the parts of the foot, a foot. But in wholes made up of similar parts, although something which is predicated of the whole may be predicated of a part (as a part of the air is air, and a part of water, water), nevertheless certain things are predicable of the whole which cannot be predicated of any of the parts; for instance, if the whole volume of water is two cubits, no part of it can be two cubits. Thus in every composite there is something which is not it itself. But, even if this could be said of whatever has a form, viz. that it has something which is not it itself, as in a white object there is something which does not belong to the essence of white; nevertheless in the form itself, there is nothing besides itself. And so, since God is absolute form, or rather absolute being, He can be in no way composite. Hilary implies this argument, when he says (De Trin. vii): "God, Who is strength, is not made up of things that are weak; nor is He Who is light, composed of things that are dim."

Reply to Objection 1: Whatever is from God imitates Him, as caused things imitate the first cause. But it is of the essence of a thing to be in some sort composite; because at least its existence differs from its essence, as will be shown hereafter, (Question 4, Article 3).

Reply to Objection 2: With us composite things are better than simple things, because the perfections of created goodness cannot be found in one simple thing, but in many things. But the perfection of divine goodness is found in one simple thing (Question 4, Article 1 and Question 6, Article 2).

Articulus 7

Argumentum 1

Ad septimum sic proceditur. Videtur quod deus non sit omnino simplex. Ea enim quae sunt a deo, imitantur ipsum, unde a primo ente sunt omnia entia, et a primo bono sunt omnia bona. Sed in rebus quae sunt a deo, nihil est omnino simplex.

Ergo deus non est omnino simplex.

Argumentum 2

Praeterea, omne quod est melius, deo attribuendum est. Sed, apud nos, composita sunt meliora simplicibus, sicut corpora mixta elementis, et elementa suis partibus.

Ergo non est dicendum quod deus sit omnino simplex.

Sed Contra

Sed contra est quod Augustinus dicit, VI de Trin., quod deus vere et summe simplex est.

Corpus

Respondeo dicendum quod deum omnino esse simplicem, multipliciter potest esse manifestum.

Primo quidem per supradicta.

Cum enim in deo non sit compositio, neque quantitativarum partium, quia corpus non est; neque compositio formae et materiae, neque in eo sit aliud natura et suppositum; neque aliud essentia et esse, neque in eo sit compositio generis et differentiae; neque subiecti et accidentis, manifestum est quod deus nullo modo compositus est, sed est omnino simplex.

Secundo, quia omne compositum est posterius suis componentibus, et dependens ex eis. Deus autem est primum ens, ut supra ostensum est.

Tertio, quia omne compositum causam habet, quae enim secundum se diversa sunt, non conveniunt in aliquod unum nisi per aliquam causam adunantem ipsa. Deus autem non habet causam, ut supra ostensum est, cum sit prima causa efficiens.

Quarto, quia in omni composito oportet esse potentiam et actum, quod in deo non est, quia vel una partium est actus respectu alterius; vel saltem omnes partes sunt sicut in potentia respectu totius.

Quinto, quia omne compositum est aliquid quod non convenit alicui suarum partium. Et quidem in totis dissimilium partium, manifestum est, nulla enim partium hominis est homo, neque aliqua partium pedis est pes. In totis vero similium partium, licet aliquid quod dicitur de toto, dicatur de parte, sicut pars aeris est aer, et aquae aqua; aliquid tamen dicitur de toto, quod non convenit alicui partium, non enim si tota aqua est bicubita, et pars eius. Sic igitur in omni composito est aliquid quod non est ipsum. Hoc autem etsi possit dici de habente formam, quod scilicet habeat aliquid quod non est ipsum (puta in albo est aliquid quod non pertinet ad rationem albi), tamen in ipsa forma nihil est alienum. Unde, cum deus sit ipsa forma, vel potius ipsum esse, nullo modo compositus esse potest.

Et hanc rationem tangit Hilarius, VII de Trin., dicens, deus, qui virtus est, ex infirmis non continetur, neque qui lux est, ex obscuris coaptatur.

Ad 1

Ad primum ergo dicendum quod ea quae sunt a deo, imitantur deum sicut causata primam causam. Est autem hoc de ratione causati, quod sit aliquo modo compositum, quia ad minus esse eius est aliud quam quod quid est, ut infra patebit.

Ad 2

Ad secundum dicendum quod apud nos composita sunt meliora simplicibus, quia perfectio bonitatis creaturae non invenitur in uno simplici, sed in multis. Sed perfectio divinae bonitatis invenitur in uno simplici, ut infra ostendetur.