On Christian Doctrine, in Four Books

Chapter 21

32. Nor can we exclude from this kind of superstition those who were called genethliaci, on account of their attention to birthdays, but are now commonly called mathematici. For these, too, although they may seek with pains for the true position of the stars at the time of our birth, and may sometimes even find it out, yet in so far as they attempt thence to predict our actions, or the consequences of our actions, grievously err, and sell inexperienced men into a miserable bondage. For when any freeman goes to an astrologer of this kind, he gives money that he may come away the slave either of Mars or of Venus, or rather, perhaps, of all the stars to which those who first fell into this error, and handed it on to posterity, have given the names either of beasts on account of their likeness to beasts, or of men with a view to confer honour on those men. And this is not to be wondered at, when we consider that even in times more recent and nearer our own, the Romans made an attempt to dedicate the star which we call Lucifer to the name and honour of Caesar. And this would, perhaps, have been done, and the name handed down to distant ages, only that his ancestress Venus had given her name to this star before him, and could not by any law transfer to her heirs what she had never possessed, nor sought to possess, in life. For where a place was vacant, or not held in honour of any of the dead of former times, the usual proceeding in such cases was carried out. For example, we have changed the names of the months Quintilis and Sextilis to July and August, naming them in honour of the men Julius Caesar and Augustus Caesar; and from this instance any one who cares can easily see that the stars spoken of above formerly wandered in the heavens without the names they now bear. But as the men were dead whose memory people were either compelled by royal power or impelled by human folly to honour, they seemed to think that in putting their names upon the stars they were raising the dead men themselves to heaven. But whatever they may be called by men, still there are stars which God has made and set in order after His own pleasure, and they have a fixed movement, by which the seasons are distinguished and varied. And when any one is born, it is easy to observe the point at which this movement has arrived, by use of the rules discovered and laid down by those who are rebuked by Holy Writ in these terms: "For if they were able to know so much that they could weigh the world, how did they not more easily find out the Lord thereof?"