Letter 160: Evodius asks how eternal reason relates to God, the Father, and the Son.

Evodius sends greetings to Bishop Augustine. Perfect reason is the reason that supplies knowledge of all things, especially of the eternal realities grasped by the intellect. Reason itself teaches and shows that this reason is eternal and ought to have been eternal. It shows that what is eternal is what neither began nor changes nor varies. It is necessary that reason be eternal, not only because it teaches and demonstrates eternal things, but much more because eternity itself cannot exist without reason. I think there would be no eternity if reason itself had not been eternal. Then reason demonstrates that God exists, or ought to exist, and that it should not be otherwise than that God exists. Whether there were people who knew this or not, since God is eternal, we must not doubt that the reason which meant to show that God had to exist is eternal, and that in showing this it shows itself to be coeternal with him. There are some things that are compelled by reason to exist in such a way that reason comes first and the effect of the thing which reason shows will exist comes afterward. For example, when the world was made, reason had it that the world should be made. Reason, therefore, is prior to the world. The things reason knew would exist then followed, so that reason is the ruler first and the operation of the world afterward. Now, since reason shows that God exists, or that it is necessary for God to exist, what shall we put before what? Reason before God? Reason before the world? Or God before reason, without which it is in no way probable that God exists? If for God to be eternal is for him to be eternal by reason, what is that reason? It is either God, or belongs to God, as reason itself teaches. If reason itself is God, then reason shows God to be reason, and these can be coeval and coeternal. If this reason is God's likeness, then it shows that reason belongs similarly to God, and this too will be coeval and coeternal. Reason itself shows that God could not similarly exist unless God existed; if reason were taken away, which it is impious even to say, there would be no God, if reason did not show that God must be. God exists, then, when his reason shows that he is God. Therefore, because God exists, there is without doubt a reason which taught that he exists. What, then, if it can be said, is first in God: reason, or God? But God will not exist unless there is reason teaching that God ought to exist. Reason also will not exist unless God exists. Nothing there is first or last. This divine nature, then, somehow has reason and God together. One generates one: either reason generates God, or God generates reason. Perhaps reason and God may be called subject and what is in the subject. God and reason are one in one. But it is well said that God generates reason, because reason demonstrates that God exists. God is understood by reason as the Son is understood by the Father, and reason by God as the Father by the Son. For reason itself with God is God. God was never without reason, nor reason without God. God exists if reason exists, and the Son exists if the Father exists; so that if reason were removed, as has been said, which may it not be lawful to say, God himself would not exist, for by his reason there is act and operation so that he is God. Let us say the same again. If reason did not exist, God did not exist; and if God does not exist, reason did not exist. Reason and God, therefore, are one eternal reality, and God and reason in the same way are eternal reality. The joining and union of reason to God and God to reason, of Father to Son and Son to Father, somehow provide each other principles and causes of existing, because one cannot exist without the other. Words fail, and whatever is said is said so that we do not remain silent. Shall we call God the offspring of reason, or reason the offspring of God, since fruit cannot exist without root, nor is root anything without fruit? Let the likeness be drawn so that some understanding of God may be signified. Even in a grain of wheat there lives a fecundating reason by which it is not allowed to be sterile; but again, if the grain of wheat did not exist, reason would have nothing from which to produce those things. Since, therefore, reason which is God either shows God to be reason or shows reason to be God, one somehow showing the other, the Father is not shown except through the Son, nor the Son except through the Father. Then the Son is, as it were, in silence when through the Father one comes to the Son, so that one is somehow hidden and the other shown. When one shows himself, he shows the other too; nor can one be known in such a way that the other lies hidden. For he says, "Whoever has seen me has seen the Father," and, "No one comes to the Father except through me," and, "No one comes to me unless the Father has drawn him." We have entered on a very steep and difficult business, trying to understand something about God while not understanding. Yet just as all things that exist are not understood and are unknowable without some form, so much more is God unknown without the Son, that is, without reason. What then? Was the Father ever without reason, irrational? Who would dare say that? God must therefore be known through reason as one from one, or one in one, and together one: because God is one, and that love which reason itself teaches must always be had, or which God commands to be shown, must necessarily be in him.

EPISTOLA 160 Scripta a. 414 aut 415. Evodius Augustino movens quaestionem de aeterna rerum ratione et Deo (nn. 1-3), sententiam suam ostendens ratione Deum revelari ut Patrem a Filio (n. 4). EVODIUS AUGUSTINO EPISCOPO, SALUTEM. Aeterna rerum ratio. 1. Perfecta ratio illa est quae omnium rerum praestat scientiam, et maxime aeternarum rerum quae intellectu comprehenduntur: hanc aeternam esse, aeternam esse debuisse; aeternum illud esse quod nec coepit, nec mutatur, nec variatur, ipsa docet atque ostendit ratio: quam necesse est esse aeternam, non solum quod aeterna doceat et demonstret, sed multo magis quod ipsa aeternitas non potest esse sine ratione; quia, arbitror, non esset aeternitas, si ratio ipsa aeterna non fuisset. Deinde Deum esse, vel esse debuisse, nec aliter fieri debere quam ut Deus esset, ratio demonstrat. Quae utique sive essent qui hoc scirent, sive non essent, tamen cum aeternus sit Deus, dubitandum non est aeternam esse rationem quae Deum esse oportuisse intenderet, et ita ut illi se demonstraret esse coaeternam. Ratio, Deum necessarium ostendens, estne ipsa Deus? 2. Sunt autem quaedam quae ratione coguntur ut sint, ut anterior sit ratio, et effectus posterior eius rei quam futuram esse ostendit ratio: ut verbi gratia, cum mundus factus est, ratio habuit ut fieret mundus. Prior ergo ratio quam mundus est. Ea ergo quae scivit ratio futura esse, subsecuta sunt, ut sit princeps ratio, postea mundi operatio. Iam nunc quoniam ratio ostendit Deum esse, vel necesse esse ut Deus esset, quid cui praeponemus? rationem Deo, aut rationem mundo, an Deum rationi, sine qua Deum nullatenus esse probabile est? si enim Deum esse aeternum, est ratione esse aeternum, quae est ratio? Ergo aut Deus est, aut Dei est, ut ipsa docet ratio: quae si ipsa est Deus, ratio ostendit Deum esse rationem, et possunt ista coaeva et coaeterna esse. Si autem Dei est similitudo haec ratio, ostendit rationem Dei esse similiter: et hoc erit coaevum et coaeternum. Deum autem esse similiter fieri non posse, nisi esset Deus, ipsa ratio ostendit: quae ratio si auferatur, quod dictu nefas est, non erit Deus, si ratio non ostenderit necesse esse Deum. Tunc ergo Deus est, cum eius ratio ostendit ut sit Deus. Deus ergo quia est: sine dubio est ratio quae docuit quia est. Connexio rationis ad Deum Deique ad rationem. 3. Quid ergo est, si dici potest, in Deo primum, ratio, an Deus? Sed Deus non erit, nisi fuerit ratio quae doceat Deum esse debere. Ratio quoque non erit, nisi Deus erit. Nihil ergo ibi primum, et postremum. Natura ergo haec divina simul quodammodo habet et rationem et Deum. Unum autem unum generat, aut ratio Deum, aut Deus rationem. Subiectum autem, aut in subiecto forte dicatur ratio et Deus. Deus et ratio unus in uno. Bene autem Deus generat rationem: quia ratio Deum esse demonstrat. Intellegitur autem Deus a ratione ut Filius a Patre, et ratio a Deo, ut Pater a Filio. Nam et ipsa ratio cum Deo Deus est. Neque enim Deus aliquando sine ratione fuit, aut ratio sine Deo. Tunc enim Deus est si est ratio, et tunc Filius est si est Pater; ut si ratio auferatur, sicut dictum est, quod dici fas non est, ne ipse quidem Deus est: per eius enim rationem est actus et operatio ut sit Deus. Rursus eadem dicamus. Si ratio non fuit, Deus non fuit; et si Deus non est, ratio non fuit. Ratio ergo et Deus sempiterna res: et Deus et ratio simili modo res sempiterna. Connexio autem atque unitio rationis ad Deum, et Dei ad rationem, Patris ad Filium, Filii ad Patrem, principia sibi quodammodo et causas existendi praestant; quia alterum sine altero esse non potest. Deficitur in verbis, et quodcumque dicitur, ad hoc dicitur, ne sileatur. Utrum autem germen rationis Deum dicamus, an Dei germen rationem, quia nec fructus sine radice esse potest, nec sine fructu radix aliquid est? (Similitudo sit ducta, ut quiddam intellegentiae de Deo signetur; vivit enim et in grano tritici ratio fecundans, qua sterile non sinitur esse: sed iterum si granum tritici non esset, ex qua re ista produceret, ratio non haberet.) Deum cognosci per Filium, aeternam eius rationem. 4. Cum igitur ratio quae Deus est, aut ostendat Deum rationem, aut rationem esse Deum, unum quodam modo alterum ostendens; non ostenditur Pater nisi per Filium, nec Filius ostenditur nisi per Patrem; et tunc quasi in silentio sit Filius, quando per Patrem venitur ad Filium, ut unum quodam modo abscondatur, alterum demonstretur: ut demonstrans se unus, demonstret et alterum, nec possit unus sciri, ut lateat alter; quia: Qui me vidit, inquit, vidit et Patrem; et: Nemo venit ad Patrem, nisi per me 1; et: Nemo venit ad me, nisi quem Pater attraxerit 2. Arduum vehementerque difficile negotium inivimus, ut aliquid de Deo non intellegentes intellegeremus. Tamen quemadmodum omnia quae sunt, sine quadam specie non intelleguntur, et incognoscibilia sunt; sic multo magis sine Filio, hoc est, sine ratione incognitus est Deus. Quid enim? an aliquando sine ratione Pater alogus fuit? Quis hoc audeat dicere? Cognoscendum itaque ratione Deum unum ex uno, vel unum in uno simul unum esse: quia unus est Deus, cui necesse est illam inesse dilectionem quam semper habendam ipsa ratio docet, vel Deus praecipit dilectionem exhibendam esse.