3 If, therefore, even with respect to creation, there are some things [the knowledge of] which belongs only to God, and others which come within the range of our own knowledge, what ground is there for complaint, if, in regard to those things which we investigate in the Scriptures (which are throughout spiritual), we are able by the grace of God to explain some of them, while we must leave others in the hands of God, and that not only in the present world, but also in that which is to come, so that God should for ever teach, and man should for ever learn the things taught him by God?
As the apostle has said on this point, that, when other things have been done away, then these three, “faith, hope, and charity, shall endure.” For faith, which has respect to our Master, endures unchangeably, assuring us that there is but one true God, and that we should truly love Him for ever, seeing that He alone is our Father; while we hope ever to be receiving more and more from God, and to learn from Him, because He is good, and possesses boundless riches, a kingdom without end, and instruction that can never be exhausted.
If, therefore, according to the rule which I have stated, we leave some questions in the hands of God, we shall both preserve our faith uninjured, and shall continue without danger; and all Scripture, which has been given to us by God, shall be found by us perfectly consistent; and the parables shall harmonize with those passages which are perfectly plain; and those statements the meaning of which is clear, shall serve to explain the parables; and through the many diversified utterances [of Scripture] there shall be heard one harmonious melody in us, praising in hymns that God who created all things.
If, for instance, any one asks, “What was God doing before He made the world?” we reply that the answer to such a question lies with God Himself. For that this world was formed perfect by God, receiving a beginning in time, the Scriptures teach us; but no Scripture reveals to us what God was employed about before this event. The answer therefore to that question remains with God, and it is not proper for us to aim at bringing forward foolish, rash, and blasphemous suppositions [in reply to it]; so, as by one's imagining that he has discovered the origin of matter, he should in reality set aside God Himself who made all things.
Source: Adversus haereses (New Advent)