In discussing the relations of the Fathers towards the astral science, we have already shown how they purged it of some of its grossest errors. But their principal service to the science remains now to be told. For amongst all the vagaries of the science of the heavens, astrology is both in theory and in practice the most deplorable. That the Fathers placed the weight of their great authority in the scale against this superstition, is one of the most praiseworthy of their achievements. At the time that the Fathers began to write, in the century just following the labors of the Apostles, astrology formed everywhere an integral part of the science of astronomy. It was taught in all the schools, Chaldean, Jewish, Grecian and Roman. Almost from the beginning the defenders of the Christian faith proceeded to attack this pernicious error, realizing how inimical it was to the spread of truth which Christ had come to impart. Already in his address to the Greeks, Tatian was heard denouncing the absurdities of Grecian astronomy and astrology. This was in the middle of the second century, just at the close of what is called the Apostolic Period. A little later, Tertullian, the famed apologist of the then flourishing African Church, placed himself on record as the uncompromising enemy of astrology. With his usual vehemence of language he declared that “of astrologers there should be no speaking even” among Christians; and went to the length of saying that “he cannot hope for heaven whose finger or wand abuses the heavens.” These and many similar utterances may be found in his Treatise on Idolatry.
With this denunciation of magic and idolatry there went hand in hand, however, a genuine respect for the proper science of the heavens. Contemporary with Tertullian, and like him one of the great Christian masters of the period, was Clement Alexandria. To the Catholic astronomer of to-day it is gratifying to find this Father of the Egyptian Church giving generous testimony to the worth of astronomical science. With just discrimination he praises astronomy as “leading the soul nearer to the creative power, as helpful to navigation and husbandry, and as making the soul in the highest degree observant, capable of perceiving the true and detecting the false.”
Father George Vincent Leahy, Astronomical Essays (1910)