14 None of us gives any consideration to the circumstance that, at the time at which we observe Easter, the sun is in the Ram, as they call a certain region of the heavenly bodies, in which the sun is, in fact, found at the beginning of the months; but whether they, choose to call that part of the heavens the Ram or anything else, we have learned this from the Sacred Scriptures, that God made all the heavenly bodies, and appointed their places as it pleased Him; and whatever the parts may be into which astronomers divide the regions set apart and ordained for the different constellations, and whatever the names by which they distinguish them, the place occupied by the sun in the first month is that in which the celebration of this sacrament behooved to find that luminary, because of the illustration of a holy mystery in the renovation of life, of which I have already spoken sufficiently. If, however, the name of Ram could be given to that portion of the heavenly bodies because of some correspondence between their form and the name, the word of God would not hesitate to borrow from anything of this kind an illustration of a holy mystery, as it has done not only from other celestial bodies, but also from terrestrial things, e.g. from Orion and the Pleiades, Mount Zion, Mount Sinai, and the rivers of which the names are given, Gihon, Pison, Tigris, Euphrates, and particularly from the river Jordan, which is so often named in the sacred mysteries.
15. But who can fail to perceive how great is the difference between useful observations of the heavenly bodies in connection with the weather, such as farmers or sailors make; or in order to mark the part of the world in which they are, and the course which they should follow, such as are made by pilots of ships or men going through the trackless sandy deserts of southern Africa; or in order to present some useful doctrine under a figure borrowed from some facts concerning heavenly bodies—and the vain hallucinations of men who observe the heavens not to know the weather, or their course, or to make scientific calculations, or to find illustrations of spiritual things, but merely to pry into the future and learn now what fate has decreed?
Source: Letters (New Advent)