Exposition of the Faith

Now the Greeks declare that all our affairs are controlled by the rising and setting and collision of these stars, viz., the sun and moon: for it is with these matters that astrology has to do. But we hold that we get from them signs of rain and drought, cold and heat, moisture and dryness, and of the various winds, and so forth, but no sign whatever as to our actions. For we have been created with free wills by our Creator and are masters over our own actions. Indeed, if all our actions depend on the courses of the stars, all we do is done of necessity: and necessity precludes either virtue or vice. But if we possess neither virtue nor vice, we do not deserve praise or punishment, and God, too, will turn out to be unjust, since He gives good things to some and afflicts others. Nay, He will no longer continue to guide or provide for His own creatures, if all things are carried and swept along in the grip of necessity. And the faculty of reason will be superfluous to us: for if we are not masters of any of our actions, deliberation is quite superfluous. Reason, indeed, is granted to us solely that we might take counsel, and hence all reason implies freedom of will.

And, therefore, we hold that the stars are not the causes of the things that occur, nor of the origin of things that come to pass, nor of the destruction of those things that perish. They are rather signs of showers and changes of air. But, perhaps, some one may say that though they are not the causes of wars, yet they are signs of them. And, in truth, the quality of the air which is produced by sun, and moon, and stars, produces in various ways different temperaments, and habits, and dispositions. But the habits are among the things that we have in our own hands, for it is reason that rules, and directs, and changes them.

It often happens, also, that comets arise. These are signs of the death of kings, and they are not any of the stars that were made in the beginning, but are formed at the same time by divine command and again dissolved. And so not even that star which the Magi saw at the birth of the Friend and Saviour of man, our Lord, Who became flesh for our sake, is of the number of those that were made in the beginning. And this is evidently the case because sometimes its course was from east to west, and sometimes from north to south; at one moment it was hidden, and at the next it was revealed: which is quite out of harmony with the order and nature of the stars.

It must be understood, then, that the moon derives its light from the sun; not that God was unable to grant it light of its own, but in order that rhythm and order may be unimpressed upon nature, one part ruling, the other being ruled, and that we might thus be taught to live in community and to share our possessions with one another, and to be under subjection, first to our Maker and Creator, our God and Master, and then also to the rulers set in authority over us by Him: and not to question why this man is ruler and not I myself, but to welcome all that comes from God in a gracious and reasonable spirit.

The sun and the moon, moreover, suffer eclipse, and this demonstrates the folly of those who worship the creature in place of the Creator, and teaches us how changeable and alterable all things are. For all things are changeable save God, and whatever is changeable is liable to corruption in accordance with the laws of its own nature.

Now the cause of the eclipse of the sun is that the body of the moon is interposed like a partition-wall and casts a shadow, and prevents the light from being shed down on us: and the extent of the eclipse is proportional to the size of the moon's body that is found to conceal the sun. But do not marvel that the moon's body is the smaller. For many declare that the sun is many times larger even than the earth, and the holy Fathers say that it is equal to the earth: yet often a small cloud, or even a small hill or a wall quite conceals it.

The eclipse of the moon, on the other hand, is due to the shadow the earth casts on it when it is a fifteen days' moon and the sun and moon happen to be at the opposite poles of the highest circle, the sun being under the earth and the moon above the earth. For the earth casts a shadow and the sun's light is prevented from illuminating the moon, and therefore it is then eclipsed.

It should be understood that the moon was made full by the Creator, that is, a fifteen days' moon: for it was fitting that it should be made complete. But on the fourth day, as we said, the sun was created. Therefore the moon was eleven days in advance of the sun, because from the fourth to the fifteenth day there are eleven days. Hence it happens that in each year the twelve months of the moon contain eleven days fewer than the twelve months of the sun. For the twelve months of the sun contain three hundred and sixty-five and a quarter days, and so because the quarter becomes a whole, in four years an extra day is completed, which is called bis-sextile. And that year has three hundred and sixty-six days. The years of the moon, on the other hand, have three hundred and fifty-four days. For the moon wanes from the time of its origin, or renewal, till it is fourteen and three-quarter days' old, and proceeds to wane till the twenty-ninth and a half day, when it is completely void of light. And then when it is once more connected with the sun it is reproduced and renewed, a memorial of our resurrection. Thus in each year the moon gives away eleven days to the sun, and so in three years the intercalary month of the Hebrews arises, and that year comes to consist of thirteen months, owing to the addition of these eleven days.

It is evident that both sun and moon and stars are compound and liable to corruption according to the laws of their various natures. But of their nature we are ignorant. Some, indeed, say that fire when deprived of matter is invisible, and thus, that when it is quenched it vanishes altogether. Others, again, say that when it is quenched it is transformed into air.

The circle of the zodiac has an oblique motion and is divided into twelve sections called zodia, or signs: each sign has three divisions of ten each, i.e. thirty divisions, and each division has sixty very minute subdivisions. The heaven, therefore, has three hundred and sixty-five degrees: the hemisphere above the earth and that below the earth each having one hundred and eighty degrees.

The abodes of the planets.

The Ram and the Scorpion are the abode of Mars: the Bull and the Scales, of Venus: the Twins and the Virgin, of Mercury: the Crab, of the Moon: the Lion, of the Sun: the Archer and the Fish, of Jupiter: Capricorn and Aquarius, of Saturn.

Their altitudes.

The Ram has the altitude of the Sun: the Bull, of the Moon: the Crab, of Jupiter: the Virgin, of Mars: the Scales, of Saturn: Capricorn, of Mercury: the Fish, of Venus.

The phases of the moon.

It is in conjunction whenever it is in the same degree as the sun: it is born when it is fifteen degrees distant from the sun: it rises when it is crescent-shaped, and this occurs twice, at which times it is sixty degrees distant from the sun: it is half-full twice, when it is ninety degrees from the sun: twice it is gibbous, when it is one hundred and twenty degrees from the sun: it is twice a full moon, giving full light, when it is a hundred and fifty degrees from the sun: it is a complete moon when it is a hundred and eighty degrees distant from the sun. We say twice, because these phases occur both when the moon waxes and when it wanes. In two and a half days the moon traverses each sign.