It is written (Romans 1:19), "That which is known of God," namely, what can be known of God by natural reason, "is manifest in them."
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 ofGod 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.
ST 1. Q12. A12