5 But those who overstep the borders, making the words of Scripture their apology for the art of casting nativities, pretend that our lives depend upon the motion of the heavenly bodies, and that thus the Chaldæans read in the planets that which will happen to us. By these very simple words “let them be for signs,” they understand neither the variations of the weather, nor the change of seasons; they only see in them, at the will of their imagination, the distribution of human destinies. What do they say in reality? When the planets cross in the signs of the Zodiac, certain figures formed by their meeting give birth to certain destinies, and others produce different destinies.
Perhaps for clearness sake it is not useless to enter into more detail about this vain science. I will say nothing of my own to refute them; I will use their words, bringing a remedy for the infected, and for others a preservative from falling. The inventors of astrology seeing that in the extent of time many signs escaped them, divided it and enclosed each part in narrow limits, as if in the least and shortest interval, in a moment, in the twinkling of an eye, to speak with the Apostle, the greatest difference should be found between one birth and another. Such an one is born in this moment; he will be a prince over cities and will govern the people, in the fullness of riches and power. Another is born the instant after; he will be poor, miserable, and will wander daily from door to door begging his bread. Consequently they divide the Zodiac into twelve parts, and, as the sun takes thirty days to traverse each of the twelve divisions of this unerring circle, they divide them into thirty more. Each of them forms sixty new ones, and these last are again divided into sixty. Let us see then if, in determining the birth of an infant, it will be possible to observe this rigorous division of time. The child is born. The nurse ascertains the sex; then she awaits the wail which is a sign of its life. Until then how many moments have passed do you think? The nurse announces the birth of the child to the Chaldæan: how many minutes would you count before she opens her mouth, especially if he who records the hour is outside the women's apartments? And we know that he who consults the dial, ought, whether by day or by night, to mark the hour with the most precise exactitude. What a swarm of seconds passes during this time! For the planet of nativity ought to be found, not only in one of the twelve divisions of the Zodiac, and even in one of its first subdivisions, but again in one of the sixtieth parts which divide this last, and even, to arrive at the exact truth, in one of the sixtieth subdivisions that this contains in its turn. And to obtain such minute knowledge, so impossible to grasp from this moment, each planet must be questioned to find its position as regards the signs of the Zodiac and the figures that the planets form at the moment of the child's birth. Thus, if it is impossible to find exactly the hour of birth, and if the least change can upset all, then both those who give themselves up to this imaginary science and those who listen to them open-mouthed, as if they could learn from them the future, are supremely ridiculous.
Source: Nine Homilies of Hexaemeron (New Advent)