De Opificio Mundi

And the greatness of the power and sovereignty of the sun has its most conspicuous proof in what has been already said: for he, being one and single has been allotted for his own share and by himself one half portion of all time, namely day; and all the other lights in conjunction with the moon have the other portion, which is called night. And when the sun rises all the appearances of such numbers of stars are not only obscured but absolutely disappear from the effusion of his beams; and when he sets then they all assembled together,

And they have been created, as Moses tells us, not only that they might send light upon the earth, but also that they might display signs of future events. For either by their risings, or their settings, or their eclipses, or again by their appearances and occultations, or by the other variations observable in their motions, men oftentimes conjecture what is about to happen, the productiveness or unproductiveness of the crops, the birth or loss of their cattle, fine weather or cloudy weather, calm and violent storms of wind, floods in the rivers or droughts, a tranquil state of the sea and heavy waves, unusual changes in the seasons of the year when either the summer is cold like winter, or the winter warm, or when the spring assumes the temperature of autumn or the autumn that of spring.

And before now some men have conjecturally predicted disturbances and commotions of the earth from the revolutions of the heavenly bodies, and innumerable other events which have turned out most exactly true: so that it is a most veracious saying that the stars were created to act as signs, and moreover to mark the seasons. And by the word seasons the divisions of the year are here intended. And why may not this be reasonably affirmed? For what other idea of opportunity can there be except that it is the time for success? And the seasons bring everything to perfection and set everything right; giving perfection to the sowing and planting of fruits, and to the birth and growth of animals.

They were also created to serve as measures of time; for it is by the appointed periodical revolutions of the sun and moon and other stars, that days and months and years are determined. And moreover it is owing to them that the most useful of all things, the nature of number exists, time having displayed it; for from one day comes the limit, and from two the number two, and from three, three, and from the notion of a month is derived the number thirty, and from a year that number which is equal to the days of the twelve months, and from infinite time comes the notion of infinite number.