Introduction to Astronomy

Since the celestial bodies surround the lower world original: "mundum inferiorem," referring to the sublunary sphere of Earth with a double embrace, it is by their natural motion that the elements of this world—which are naturally annexed to them—undergo a circular resolution of one into the other. This process is the cause of all generation and corruption The Aristotelian concept that the birth of one thing is the death of another, for nature follows this course. Since, therefore, celestial motion is the cause of elementary resolution, and this resolution is the cause of effects and corruptions, it is necessary that these same effects and destructions follow the specific celestial motions. For the corruption of one thing is the generation of another: indeed, the burning of wood is the effect of charcoal; the corruption of charcoal generates ash. Whence among philosophers original: "phos," abbreviation for philosophos there is a common saying: the natural motion of the stars is perpetual, and the effect of nature is perpetual.

¶ The opinion of the second sect: that the stars have leadership over general and universal things, such as the genera and species of things, the alterations of the seasons, the resolutions of elements, and things of that kind; but not over individual or singular things, nor their specific parts or properties. Against these, arguments have been aired in all philosophy. Since every body of this world is composed of the four elements, the motions of the stars are felt in every body, as they preside over them and these bodies must follow them. Since celestial motions are the cause of elementary resolution, and resolution is the cause of generations, it follows that these same generations are also the effect of those motions. Likewise, since nothing belongs to genera or species that is foreign to individuals, when they proceed from the substance of an animal or a man, the properties and accidents term: accidents non-essential qualities like color or mood must also have leadership; and just as they provide leadership to the substance, they must provide it to the condition of color and the condition of affection, since they direct the genera and species of all things.

¶ The third sect of a more subtle opinion: by a certain similarity of arguments, they labor to strip away all efficacy from astrology, which, by assuming a part, denies that the stars have influence over "either-or" term: vtrumlibet contingent events that could go either way, like free will effects. Therefore, when it cannot achieve this, it happens in both ways: exhausted by such great labor, it fails at the feast. We, however, having first explained the opinion of those who deny it, and immediately contradicting that same opinion, will affirm the "either-or"; then we will demonstrate that even the motions of the stars lead to "either-or" outcomes. For those who, assuming the "either-or," try to render astrology vain, say: Since there are three modes for all things in this world—necessary (as it is impossible for fire not to be hot), impossible (as for it to be cold), and either-or (as for a man to write)—the effect of the stars can never be visible. Thus, the office of astrology is superfluous.

Because some of the first and second rank of astrologers could not respond sufficiently to this proposition due to a less firm knowledge, they were led into the inconvenience of the conclusion: they fled so far as to believe nothing was "either-or" i.e., they became total determinists to save their craft. Thus, while they tried to flee a small error, they fell into a greater one. And since one was the cause of the other, the heap of error grew with a double mound. It seemed to them, therefore, that there are only two modes: the necessary and the impossible. For whatever is to be in the future, they say, is between "it is" and "it is not." If it is toward being and not toward non-being, then it is necessary to be and impossible not to be; for being and non-being are contradictories about the same thing at the same time and are never both true: one is always true, the other always false. Therefore, what is so, is necessary; what is not, is impossible. Whence nothing is left to the deliberation of men, but they either act compelled by necessity or do not act because they are prohibited by impossibility.

¶ The philosopher likely referring to Aristotle, meeting these men, first refuted their verbosity with strong arguments, and subjoining the affirmation of the "either-or" by an argument, he said: Everything that is "either-or" follows either the necessary or the impossible.