53 For in human affairs You have set before us many things of such a sort, that though we do not know their cause, yet the effect is not unknown; and reverence inculcates faith, where ignorance is inherent in our nature. Thus when I raised to Your heaven these feeble eyes of mine, my certainty regarding it was limited to the fact that it is Yours. For seeing therein these orbits where the stars are fixed, and their annual revolutions, and the Pleiades and the Great Bear and the Morning Star, each having their varied duties in the service which is appointed them, I recognise Your presence, O God, in these things whereof I cannot gain any clear understanding.
And when I view the marvellous swellings of Your sea, I know that I have failed to comprehend not merely the origin of the waters but even the movements of this changeful expanse; yet I grasp at faith in some reasonable cause, although it is one that I cannot see, and fail not to recognise You in these things also, which I do not know. Furthermore, when in thought I turn to the earth, which by the power of hidden agencies causes to decay all the seeds which it receives, quickens them when decayed, multiplies them when quickened, and makes them strong when multiplied; in all these changes I find nothing which my mind can understand, yet my ignorance helps towards recognising You, for though I know nothing of the nature that waits on me, I recognise You by actual experience of the advantages I possess.
Moreover, though I do not know myself, yet I perceive so much that I marvel at You the more because I am ignorant of myself. For without understanding it, I perceive a certain motion or order or life in my mind when it exercises its powers; and this very perception I owe to You, for though You deny the power of understanding my natural first beginning, yet You give that of perceiving nature with its charms. And since in what concerns myself I recognise You, ignorant as I am, so recognising You I will not in what concerns You cherish a feebler faith in Your omnipotence, because I do not understand. My thoughts shall not attempt to grasp and master the origin of Your Only-begotten Son, nor shall my faculties strain to reach beyond the truth that He is my Creator and my God.
Source: On the Trinity (New Advent)