"Fully"—entirely. We can partly understand it. We know what one God is and we know what three persons are; but how these two things go together is the part we do not understand—the mystery.
*31 Q. What is a mystery? A. A mystery is a truth which we cannot fully understand.
"A truth," that is, a revealed truth—one made known to us by God or His Church. It is a truth which we must believe though we cannot understand it. Let us take an example. When a boy goes to school he is taught that the earth is round like an orange and revolving in two ways, one causing day and night and the other producing the seasons: spring, summer, autumn, winter. The boy goes out into the country where he sees miles of level land and mountains thousands of feet in height. Again he goes out on the ocean where sailors tell him it is several miles in depth.
Now he may say: how can the earth be round if deep valleys, high mountains, and level plains prove to my senses the very opposite, and the countless things at rest upon its surface tell me it is motionless. Yet he believes even against the testimony of his senses that the earth is round and moving, because his teacher could have no motive in deceiving him; knows better than he, having learned more, and besides has been taught by others who after long years of careful study and research have discovered these things and know them to be true. If therefore we have to believe things that we do not understand on the authority of men, why should we not believe other truths on the authority of God? Yes, we must believe Him. If a boy knew all his teacher knew there would be no need of his going to school; he would be the equal in knowledge of his teacher, and if we knew all that God knows we would be as great as He. As well might we try to empty the whole ocean into the tiny holes that children dig in the sand by its shore, as fully to comprehend the wisdom of God. This is the mistake unbelievers make when they wish to understand with their limited intelligence the boundless knowledge and mysterious ways of God, and when they cannot understand refuse to believe. Are they not extremely foolish? Would you not ridicule the boy who refuses to believe that the earth is round and moving because he cannot understand it? As he grows older and learns more he will comprehend it better; so we, when we leave this world and come into the presence of God, shall see clearly many things that are unintelligible now. For the present, we have only to believe them on the authority of God teaching us. Another example. We take two little black seeds that look just alike and place them in the same kind of soil; we put the same kind of water upon them; they have the same sunlight and air, and yet when they grow up one has a red flower and one a blue. Where did the red and where did the blue come from? From the black seed, or the brown soil, or the pure water, air and sunlight? We do not know. It is there, and that is all. We see it and believe it, though we do not understand it.
So if we refuse to believe everything we do not understand, we shall soon believe very little and make ourselves ridiculous.
Lesson 4
ON CREATION
This lesson treats of God bringing everything into existence. The chief things created may be classed as follows: (1) The things that simply exist, as rocks, and minerals—gold, silver, iron, etc. (2) Things that exist, grow, and live like plants and trees. (3) Things that grow, live, and feel, like animals. (4) Things that grow, live, feel, and understand, like men. Besides these we have the sun, moon, stars, etc.; all things too that we can see, and also Heaven, Purgatory, Hell, and good and bad angels. All these are the works of God's creation. All these He has called into existence by merely wishing for them.
*32 Q. Who created Heaven and earth, and all things? A. God created Heaven and earth, and all things.
"Heaven," where God is and will always be. It means, too, everything we see in the sky above us. "Earth," the globe on which we live.
*33 Q. How did God create Heaven and earth? A. God created Heaven and earth from nothing, by His word only; that is, by a single act of His all-powerful will.