1 Objection 1: It seems that by natural reason we cannot know God in this life. For Boethius says De Consol. v) that reason does not grasp simple form. But God is a supremely simple form, as was shown above Question 3, Article 7). Therefore natural reason cannot attain to know Him.
1 Ad duodecimum sic proceditur. Videtur quod per naturalem rationem Deum in hac vita cognoscere non possimus. Dicit enim Boetius, in libro de Consol., quod ratio non capit simplicem formam. Deus autem maxime est simplex forma, ut supra ostensum est. Ergo ad eius cognitionem ratio naturalis pervenire non potest.
2 Objection 2: Further, the soul understands nothing by natural reason without the use of the imagination. But we cannot have an imagination of God, Who is incorporeal. Therefore we cannot know God by natural knowledge.
2 Praeterea, ratione naturali sine phantasmate nihil intelligit anima, ut dicitur in III de anima. Sed Dei, cum sit incorporeus, phantasma in nobis esse non potest. Ergo cognosci non potest a nobis cognitione naturali.
3 Objection 3: Further, the knowledge of natural reason belongs to both good and evil, inasmuch as they have a common nature. But the knowledge of God belongs only to the good; for Augustine says De Trin. i): The weak eye of the human mind is not fixed on that excellent light unless purified by the justice of faith. Therefore God cannot be known by natural reason.
3 Praeterea, cognitio quae est per rationem naturalem, communis est bonis et malis, sicut natura eis communis est. Sed cognitio Dei competit tantum bonis, dicit enim Augustinus, I de Trin., quod mentis humanae acies in tam excellenti luce non figitur, nisi per iustitiam fidei emundetur. Ergo Deus per rationem naturalem cognosci non potest.
4 On the contrary, It is written Rm. 1, 19), That which is known of God, namely, what can be known of God by natural reason, is manifest in them.
4 Sed contra est quod dicitur Rom. I, quod notum est Dei, manifestum est in illis, idest, quod cognoscibile est de Deo per rationem naturalem.
5 I answer that, Our natural knowledge begins from sense. Hence our natural knowledge can go as far as it can be led by sensible things. But our mind cannot be led by sense so far as to see the essence of God; because the sensible effects of God do not equal the power of God as their cause. Hence from the knowledge of sensible things the whole power of God cannot be known; nor therefore can His essence be seen. But because they are His effects and depend on their cause, we can be led from them so far as to know of God whether He exists, and to know of Him what must necessarily belong to Him, as the first cause of all things, exceeding all things caused by Him. Hence we know that His relationship with creatures so far as to be the cause of them all; also that creatures differ from Him, inasmuch as He is not in any way part of what is caused by Him; and that creatures are not removed from Him by reason of any defect on His part, but because He superexceeds them all.
5 Respondeo dicendum quod naturalis nostra cognitio a sensu principium sumit, unde tantum se nostra naturalis cognitio extendere potest, inquantum manuduci potest per sensibilia. Ex sensibilibus autem non potest usque ad hoc intellectus noster pertingere, quod divinam essentiam videat, quia creaturae sensibiles sunt effectus Dei virtutem causae non adaequantes. Unde ex sensibilium cognitione non potest tota Dei virtus cognosci, et per consequens nec eius essentia videri. Sed quia sunt eius effectus a causa dependentes, ex eis in hoc perduci possumus, ut cognoscamus de Deo an est; et ut cognoscamus de ipso ea quae necesse est ei convenire secundum quod est prima omnium causa, excedens omnia sua causata. Unde cognoscimus de ipso habitudinem ipsius ad creaturas, quod scilicet omnium est causa; et differentiam creaturarum ab ipso, quod scilicet ipse non est aliquid eorum quae ab eo causantur; et quod haec non removentur ab eo propter eius defectum, sed quia superexcedit.
6 Reply to Objection 1: Reason cannot reach up to simple form, so as to know what it is; but it can know whether it is.
6 Ad primum ergo dicendum quod ratio ad formam simplicem pertingere non potest, ut sciat de ea quid est, potest tamen de ea cognoscere, ut sciat an est.
7 Reply to Objection 2: God is known by natural knowledge through the images of His effects.
7 Ad secundum dicendum quod Deus naturali cognitione cognoscitur per phantasmata effectus sui.
8 Reply to Objection 3: As the knowledge of God's essence is by grace, it belongs only to the good; but the knowledge of Him by natural reason can belong to both good and bad; and hence Augustine says Retract. i), retracting what he had said before: I do not approve what I said in prayer, God who willest that only the pure should know truth. For it can be answered that many who are not pure can know many truths, that is, by natural reason.
8 Ad tertium dicendum quod cognitio Dei per essentiam, cum sit per gratiam, non competit nisi bonis, sed cognitio eius quae est per rationem naturalem, potest competere bonis et malis. Unde dicit Augustinus, in libro Retractationum, non approbo quod in oratione dixi, Deus, qui non nisi mundos verum scire voluisti, responderi enim potest, multos etiam non mundos multa scire vera, scilicet per rationem naturalem.