Summa Theologica, Part I, question 2, article 3

Whether God Exists

English Text

We proceed to the third article. It seems that God does not exist. note 1

1. This is because if one of two contraries were infinite, it would totally destroy the other. note 2
But we understand as implied in the word God that God is an infinite good.
If, then, God did exist, no evil would be found.
But evil is found in the world.
Therefore, there is no God.

2. Moreover, that which can be completed by fewer principles, is not brought about by a greater number.
But if we suppose that God does not exist, it seems that all the things that appear in the world can be completed by other principles.
This is because natural things can be led back to one principle, which is nature.
whereas those things that exist because of a decision may be led back to the principle which is the human reason or will.
Therefore there is no need to suppose that God exists.

But on the contrary, there is that which is said in Exodus 3, 14, by the person of God, "I am who am."

I answer, that is should be said that it can be proved that God exists in five ways.

The first and more manifest way is that which takes motion as its starting point.
It is certain and it stands apparent from the senses, that some things in this world are moved.
Everything which is moved, is moved by another.
It is certain and it stands apparent from the senses, that some things in this world are moved.
Everything which is moved, is moved by another.
Nothing indeed is moved, except insofar as it is in potency to that to which it is moved:
One thing moves another insofar as that one thing is in act.
To move something is nothing other than to lead something from potency to act:
however, something cannot be led from potency to act except for some being in act: as that which is hot in act, such as fire, makes wood, which is hot in potency, to be hot in act, and thereby moves and alters it.
It is not possible for the same thing at the same time to be in act and in potency in the same respect, but only in different respects:
that which is hot in act, cannot at the same time be hot in potency, but is at the same time cold in potency.
Thus it is impossible that in the same respect and in the same way something would be that which moves another and that which is moved, or that it should move itself. Everything that is moved, has to be moved by another. If therefore that by which a thing is moved, itself is mvoed, it in turn must be moved by another, and that then moved by another.
But this cannot go on to infinity:
for then there would not be any first thing that moves other things;
and consequently neither would there be any other thing that causes movement, because secondary movers do not move other things unless it is by their being moved by the first mover, as a stick does not move another thing unless is it moved by a hand.
Thus it is necessary to come to some first mover, which is not moved by another: and all men understand this as God.

The second way is by reason of an efficient cause.
We find in these sensibile things that there is an order of efficient causes:
We do not encounter a situation, or is it even possible, in which something is the efficient cause of its own self;
in such a case the thing would be prior to itself, which is impossible.
It is not possible to go on to infinity in effecient causes.
In all ordered efficient causes, the first is the cause of the one in the middle, and the middle is the cause of the last one, whether there is only one or many in the middle:
when the cause is removed, the effect is removed:
thus, if there were not a first in efficient causes, there would be no last or middle one.
But if we go on to infinity in efficient causes, there will be no first cause:
and neither will there be an ultimate cause, nor efficient causes in the middle: which is obviously false.
Therefore it is necessary to suppose that there is a first efficient cause: and all men call this God.

The third way starts from that which is possible and that which is necessary: it goes like this.
We find that some thing are capable of being or of not being:
some things are found to come into existence and go out of existence, and consquently they are possible either to be or not to be.
It is impossible that all such things would always exist: for that for which it is possible not to exist, at some time does not exist.
If therefore all things are such that it is possible not to exist, at one time there were no things.
But if this is true, there would still be nothing:
because that which does not exist, does not begin to exist except by something that does exist;
if therefore there was no being, it would have been impossible for anything to begin to exist, and there would still be nothing: which is obviously false.
Therefore, not all beings are merely possible beings: but among things there must be something necessary.
Now, everything that is necessary either has the cause of its necessity in something else, or it does not have a cause for its necessity.
It is not possible to go on to infinity in necessary things, which have a cause for their necessity, just as it is impossible to go on to infinity in efficient causes, as has been shown.
Therefore, we must suppose that there is something that is necessary on its own account, something that does not have the cause of its necessity in something else, but which is rather the cause of necessity for other things: which all men call God.

The fourth way is taken from the degrees that are found among things.
For among things one finds that there is something more good and something less good, true, and noble; and the same applies to other such features.
But more and less are said of diverse things according to how in different ways they approach something which is to the greatest degree: such as that which is more hot, more closely approaches that which is most hot.
Therefore, there is something which is most true, and best, and noblest, and which consequently exists to the greatest degree:
for the things which are most true and beings to the greatest degree, as Aristotle writes in Metaphysics II.
That which is said to be the greatest in some respect in a particular genus, is the cause of all things things that belong to the genus: just as fire, which is the hottest, is the cause of all hot things, as it says in the same book.
Thus, there is something which is the cause of existence to all beings, and the cause of goodness and any perfection whatsoever: and we call this God.

The fifth way is taken from the governance of things.
We see that some things that have no cognition, namely, natural bodies, work toward an end:
this is apparent from the fact that always or most often they work in the same way, so that they achieve that which is best; hence it is evident that they reach the end not by chance but by intention.
Those things that do not have cognition, do not tend to an end inless they are directed by something that knows and understands, as an arrow is directed by an archer.
Thus, there is something intelligent, by which all natural things are ordered to an end:
and we call this God.

TO THE FIRST OBJECTION, it should be said, as Saint Augustine said in the Enchiridion:
God, because he is most good, would not in any way allow anything evil in his works, unless he were so omnipotent and good that he could do good even from that which is evil.
It belongs to God's infinite goodness that he permits evil things to exist and draws good things from them.

TO THE SECOND OBJECTION, it should be said that, seeing that nature works in view of a determinate end under the direction of a higher agent, that things things that occur by nature should be led back to God as to their first cause.
Likewise, even those things that happen by decision, have to be reduced to some higher cause that is not the human reason or will:
for those things are susceptible to change and admit shortcomings; all things that can be moved and which may fall short must be led back to some first principle that is immovable and necessary on its own account, as was shown in the main portion of this article.

Latin Text

Ad tertium sic proceditur.
Videtur quod Deus non sit.

1. Quia si unum contrarium fuerit infinitum, totaliter destruetur aliud.
Sed hoc intelligitur in hoc nomine Deus, scilicet quod sit quoddam bonum infinitum.
Si ergo Deus esset, nullum malum inveniretur.
Invenitur autem malum in mundo.
Ergo Deus non est.

2. Praeterea, quod potest compleri per pauciora principia, non fit per plura.
Sed videtur quod omnia quae apparent in mundo, possunt compleri per alia principia, supposito quod Deus non sit;
quia ea quae sunt naturalia, reducuntur in principium quod est natura;
ea vero quae sunt a proposito, reducuntur in principium quod est ratio humana vel voluntas.
Nulla igitur necessitas est ponere Deum esse.

SED CONTRA, est quod dicitur Exodi 3, 14, ex persona Dei: Ego sum qui sum.

RESPONDEO dicendum quod Deum esse quinque viis probari potest.

Prima autem et manifestior via est, quae sumitur ex parte motus.
Certum est enim, et sensu constat, aliqua moveri in hoc mundo.
Omne autem quod movetur, ab alio movetur.
Nihil enim movetur, nisi secundum quod est in potentia ad illud ad quod movetur:
movet autem aliquid secundum quod est actu.
Movere enim nihil aliud est quam educere aliquid de potentia in actum:
de potentia autem non potest aliquid reduci in actum, nisi per aliquod ens in actu:
sicut calidum in actu, ut ignis, facit lignum, quod est calidum in potentia, esse actu calidum, et per hoc movet et alterat ipsum.
Non autem est possibile ut idem sit simul in actu et potentia secundum idem, sed solum secundum diversa:
quod enim est calidum in actu, non potest simul esse calidum in potentia, sed est simul frigidum in potentia.
Impossibile est ergo quod, secundum idem et eodem modo, aliquid sit movens et motum, vel quod moveat seipsum.
Omne ergo quod movetur, oportet ab alio moveri.
Si ergo id a quo movetur, moveatur, oportet et ipsum ab alio moveri; et illud ab alio.
Hic autem non est procedere in infinitum:
quia sic non esset aliquod primum movens;
et per consequens nec aliquod aliud movens, quia moventia secunda non movent nisi per hoc quod sunt mota a primo movente, sicut baculus non movet nisi per hoc quod est motus a manu.
Ergo necesse est devenire ad alquod primum movens, quod a nullo movetur: et hoc omnes intelligunt Deum.

Secunda via est ex ratione causae efficientis. Invenimus enim in istis sensibilibus esse ordinem causarum efficientium:
nec tamen invenitur, nec est possibile, quod aliquid sit causa efficiens sui ipsius; quia sic esset prius seipso, quod est impossibile.
Non autem est possibile quod in causis efficientibus procedatur in infinitum.
Quia in omnibus causis efficientibus ordinatis, primum est causa medii, et medium est causa ultimi, sive media sint plura sive unum tantum:
remota autem causa, removetur effectus:
ergo, si non fuerit primum in causis efficientibus, non erit ultimum nec medium.
Sed si procedatur in infinitum in causis efficientibus, non erit prima causa efficiens:
et sic non erit nec effectus ultimus, nec causae efficientes mediae: quod patet esse falsum.
Ergo est necesse ponere aliquam causam efficientem primam: quam omnes Deum nominat.

Tertia via est sumpta ex possibili et necessario: quae talis est.
Invenimus enim in rebus qauedam quae sunt possibilia esse et non esse:
cum quaedam inveniantur generari et corrumpi, et per consequens possibilia esse et non esse.
Impossibile est autem omnia quae sunt talia, semper esse: quia quod possibile est non esse, quandoque non est.
Si igitur omnia sunt possibilia non esse, aliquando nihil fuit in rebus.
Sed si hoc est verum, etiam nunc nihil esset:
quia quod non est, non incipit esse nisi per aliquid quod est;
si igitur nihil fuit ens, impossibile fuit quod aliquid inciperet esse, et sic modo nihil esset: quod patet esse falsum.
Non ergo omnia entia sunt possibilia: sed oportet aliquid esse necessarium in rebus.
Omne autem necessarium vel habet causam suae necessitatis aliunde, vel non habet.
Non est autem possibile quod procedatur in infinitum in necessariis, quae habent causam suae necessitatis sicut nec in causis efficientibus, ut probatum est.
Ergo necesse est ponere aliquid quod sit per se necessarium, non habens causam necessitatis aliunde, sed quod est causa necessitatis aliis: quod omnes dicunt Deum.

Quarta via sumitur ex gradibus qui in rebus inveniuntur.
Invenitur enim in rebus aliquid magis et minus bonum, et verum, et nobile; et sic de aliis huiusmodi.
Sed magis et minus dicuntur de diversis secundum quod appropinquant diversimode ad aliquid quod maxime est: sicut magis calidum est, quod magis appropinquat maxime calido.
Est igitur aliquid quod est verissimum, et optimum, et nobilissimum, et per consequens maxime ens:
nam quae sunt maxime vera, sunt maxime entia, ut dicitur II Metaphys.
Quod autem dicitur maxime tale in aliquo genere, est causa omnium quae sunt illius generis: sicut ignis, qui est maxime calidus, est causa omnium calidorum, ut in eodem libro dicitur.
Ergo est aliquid quod omnibus entibus est causa esse, et bonitatis, et cuiuslibet perfectionis: et hoc dicimus Deum.

Quinta via sumitur ex gubernatione rerum.
Videmus enim quod aliqua quae cognitionis carent, scilicet corpora naturalia, operantur propter finem:
quod apparet ex hoc quod semper aut frequentius eodem modo operantur, ut consequantur id quod est optimum; unde patet quod non a casu, sed ex intentione perveniunt ad finem.
Ea autem quae non habent cognitionem, non tendunt in finem nisi directa ab aliquo cognoscente et intelligente, sicut sagitta a sagittante.
Ergo est aliquid intelligens, a quo omnes res naturales ordinantur ad finem:
et hoc dicimus Deum.

AD PRIMUM ergo dicendum quod, sicut dicit Augustinus in Enchiridio:
Deus, cum sit summe bonus, nullo modo sineret aliquid mali esse in operibus suis, nisi esset adeo omnipotens et bonus, ut bene faceret etiam de malo.
Hoc ergo ad infinitam Dei bonitatem pertinet, ut esse permittat mala, et ex eis eliciat bona.

AD SECUNDUM dicendum quod, cum natura propter determinatum finem operetur ex directione alicius superioris agentis, necesse est ea quae a natura fiunt, etiam in Deum reducere, sicut in primam causam.
Similiter etiam quae ex proposito fiunt, oportet reducere in aliquam altiorem causam, quae non sit ratio vel voluntas humana:
quia haec mutabilia sunt et defectabilia;
oportet autem omnia mobilia et deficere possibilia reduci in aliquod primum principium immobile et per se necessarium, sicut ostensum est (in c.).

Commentary and notes

note 1: The method used by Saint Thomas is that of dialectics. In any question in which there are different points of view, Thomas presents the arguments on both sides. It is sometimes confusing to the reader when he finds at the beginning of any article that St. Thomas Aquinas is arguing, for example, that God does not exist. The attentive reader of Aquinas will note that he takes as much care in presenting the opposite point of view as he does his own. He avoids "strawman arguments", which is the practice of misrepresenting an opponent's point of view in order to argue against the misrepresentation, instead of grappling with the issues themselves. During the reformation, some Protestants would actually use Thomas' objections as arguments.

note 2: There are four ways in which things can be opposed to each other. 1/ contradiction -Two statements or propositions can be opposed to one another as contradictories. The relation is called in greek antiphasis; 2/ privation - which is the state of not possessing something which could be possessed, and this relation might be more commonly expressed as "deprivation", and is called in greek steresis; 3/ contrariety - contraries are two things the existence of either excluding the other - and this relation is called in Greek enantiotes; 4/relation - called in greek pros ti. [cf. Aristotle's Metaphysics, Book X, 1055a3-b30.]