[By Theology] I simply mean the Science of God, or the truths we know about God put into system; just as we have a science of the stars, and call it astronomy, or of the crust of the earth, and call it geology.
For instance, I mean, for this is the main point, that, as in the human frame there is a living principle, acting upon it and through it by means of volition, so, behind the veil of the visible universe, there is an invisible, intelligent Being, acting on and through it, as and when He will. Further, I mean that this invisible Agent is in no sense a soul of the world, after the analogy of human nature, but, on the contrary, is absolutely distinct from the world, as being its Creator, Upholder, Governor, and Sovereign Lord. Here we are at once brought into the circle of doctrines which the idea of God embodies. I mean then by the Supreme Being, one who is simply self-dependent, and the only Being who is such; moreover, that He is without beginning or Eternal, and the only Eternal; that in consequence He has lived a whole eternity by Himself; and hence that He is all-sufficient, sufficient for His own blessedness, and all-blessed, and ever-blessed. Further, I mean a Being, who, having these prerogatives, has the Supreme Good, or rather is the Supreme Good, or has all the attributes of Good in infinite intenseness; all wisdom, all truth, all justice, all love, all holiness, all beautifulness; who is omnipotent, omniscient, omnipresent; ineffably one, absolutely perfect; and such, that what we do not know and cannot even imagine of Him, is far more wonderful than what we do and can. I mean One who is sovereign over His own will and actions, though always according to the eternal Rule of right and wrong, which is Himself. I mean, moreover, that He created all things out of nothing, and preserves them every moment, and could destroy them as easily as He made them; and that, in consequence, He is separated from them by an abyss, and is incommunicable in all His attributes. And further, He has stamped upon all things, in the hour of their creation, their respective natures, and has given them their work and mission and their length of days, greater or less, in their appointed place. I mean, too, that He is ever present with His works, one by one, and confronts every thing He has made by His particular and most loving Providence, and manifests Himself to each according to its needs: and has on rational being imprinted the moral law, and given them power to obey it, imposing on them the duty of worship and service, searching and scanning them through and through with His omniscient eye, and putting before them a present trial and a judgment to come.
John Henry Cardinal Newman, The Idea of a University, London: Longmans, Green, and Co., 1893, 61-63.