Those words, And let them be for signs, have various interpretations. Some refer them to the celestial signs—that is, to those forty-eight images and figures of the stars marked out in the heaven and described by the Astronomers; others to the signs of the festival days which the Jews kept with yearly solemnity, the observance of which days depended on the course of the moon. Some think those words pertain to the signs of natural effects—of fair weather, rain, winds, barrenness, health, diseases, of sowing, sailing, cutting, and healing; concerning which Pliny writes copiously and clearly in book 18, chapter 35. There are also those who hold that by those words are denoted certain supernatural signs and miracles once produced in the heavens and stars—such, namely, as came to pass in the time of Joshua, of Moses, of Hezekiah, and of the Passion of our Lord; and such as the Lord foretold would come to pass just before the day of Judgment, in those words, There shall be signs in the sun, the moon, and the stars. Lastly, there were not lacking those who would refer those words, And let them be for signs, to astrological divination—by which, namely, from the observation of the heavenly bodies, future events of things are said to be able to be foreknown and foretold. For thus Origen thought these words were to be interpreted and understood, as Eusebius reports in the sixth book of the Preparation for the Gospel, chapter 9; and the most vain and most lying of mortals, the Astrologers whom they call Judiciary, claim that these words of Moses lend great credit to their astromancy and add[ed] authority [to it]...³

...boast that they add [authority to their astromancy]. Wherefore Basil, in his exposition of these words, refuted astrologers of this kind in a discourse quite long and accurate; and that very many other writers, both Greek and Latin, did the same is clear from their commentaries on Genesis. Wherefore we, stirred and moved by the most grave words of God set down in many places of divine Scripture against the Astrologers, and provoked by the example of the holy Fathers, and kindled with a most just hatred against them on account of the fraudulent and pernicious fictions of the Astrologers—and also because that disputation seems sufficiently to pertain to the doctrine of the heavens and the heavenly bodies which we have undertaken to deliver in this book—have thought that the labor here undertaken would not be in vain, nay, that our pains would be very usefully bestowed, if we should spend the remaining part of this book in shaking and overthrowing the divinations of the Astrologers. But, lest by the abundance of the matter, or by hatred of so impious a falsehood, the disputation proceed beyond our purpose, we shall set a measure to the treatment, handling only the chief heads, and those which strike and cut down the Astrologers more nearly and more forcibly.⁴

There was, within the memory of our fathers, Giovanni Pico della Mirandola, a man illustrious in nobility of birth, but most noble in brilliance of genius and learning, and, in fine, greater than all our praise, who wrote twelve books against the Astrologers—acutely indeed, and learnedly and copiously, but from the reading of which the prolixity of the work deters many. Others complain that not a few things are treated in them which are foreign to the cause defended, weak, and superfluous; there are also those who desire a more combative and robust kind of disputing, and would wish the adversary to be pressed more sharply and urged more vehemently. But, though that work does not have all the numbers of perfection, nor is free from all reprehension (for to which of mortals has that befallen?), it will yet be, for every age, a noble and glorious monument of that most excellent genius. We, however, that we may satisfy even the peevish and fastidious reader, will devote ourselves to this one cause, will press it, will cleave to it, and with our whole heart will apply ourselves to the defense of the truth and the refutation of the falsity of astrological predictions. And although we shall be engaged in a rich and very fruitful subject, we shall yet be the briefer for this, that we shall employ not all the things that could in any way be said, but only those fitter and firmer for the cause: for we desire to seem and to be not so much copious as strong in storming and routing the Astrologers. Now there are four things to be treated in this our disputation with the Astrologers: for first we shall teach that astrological divination is contrary to the most true doctrine contained in the sacred writings and in the Ecclesiastical discipline; then we shall demonstrate that it is also opposed to right reason and true philosophy; next we shall prove that the stars are not only not the efficient causes of all future things, but are not even signs that foreknow and foreshow all future things; and lastly we shall show what the cause is why the predictions of certain Astrologers have been found true both of old, and sometimes today turn out true.⁵