You are here

A Critique to Astrology from "De Civitate Dei"


The City of God, Book V, cc. 1-7I


1. The existence of the Roman empire and of all kingdoms is not a matter of chance nor of the position of the stars.

The cause, then, of the greatness of the Roman empire is neither chance nor fate, as these words are employed whether by the judgment, or by mere opinion of those who say that things happen by chance when they have no causes, or no cause derived from a rational pattern, and that things happen by fate when they happen not by the will of God or of men, but by the compulsion of a certain pattern. Without any doubt, it is by divine providence that human kingdoms are set up. If any one ascribes them to “fate” because he uses that term for the will or power of God, let him maintain his conviction but correct his language. Why does he not say at the start what he will say later when someone asks him what he means by “fate”? For when men hear this word, ordinary usage leads them to think of nothing but the influence of the position of the stars at the moment when a child is born, or conceived. Some make this independent of the will of God, while others maintain that it depends upon his will.

Those, however, who believe that the stars, apart from the will of God, determine what we do, what goods we have, or what evils we suffer, must be thrown out of court, not only by adherents of the true religion, but also by those who choose to worship gods of any sort, false gods though they be. For what is the effect of this belief except to persuade men not to worship or pray to any god at all? Our present argument is not directed against the supporters of this view, but against those who, in defense of those beings that they think are gods, make war on the Christian religion.

But as for those who make the position of the stars depend upon the will of God, while the stars somehow decree what sort of man each shall be, what good shall come his way, and what evil shall befall him, they do a great wrong to heaven if they hold that the sovereign power of God has handed over to the aforesaid stars the power of making these decrees of their own choice. For they suppose that it is resolved in heaven, as in some exalted senate met in its refulgent senate-house, that crimes are to be committed, such crimes that if any earthly state had decreed them, all mankind would properly have decreed its destruction. Moreover, how is any room left for God to pass judgment on the deeds of men, if they are subject to astrological forces, and God is Lord both of stars and men? Or they may say that the stars have received their power from the supreme God, and do not make their decrees of their own will, but simply obey his commands in imposing compulsion upon men. Are we then to adopt a view of God himself that it seemed highly improper to adopt in regard to the will of the stars?

But sometimes it may be said that the stars portend, but do not cause these deeds, so that their position, which foretells the future, is a kind of communication, not an active force. This view has been held by men of no ordinary learning. But the astrologers are not in the habit of saying, for instance: “Mars in this position portends a murderer,” but “makes a murderer.” However, let us grant that they do not use the proper terms, and that they ought to take from the philosophers the correct way of stating the facts that they think they find noted in the position of the stars. How is it that they have never been able to explain why there is such diversity in the life of twins: in their actions, their fortunes, their professions, their trades, their honors and in all the other things pertaining to human life and even in their death? It commonly happens that in these respects the twins resemble many strangers more than they resemble each other. And yet in birth they were separated by a very brief interval of time, and in conception they were begotten at one moment, by one act of intercourse.

2. Similarity and dissimilarity in the health of twins

Cicero says that Hippocrates, the renowned physician, has left a record of two brothers who fell sick together. Their disease grew worse at the same time, then better, hence he suspected that they were twins. Posidonius the Stoic, who was much interested in astrology, used to assert that this happened because they were born, and were conceived, under the same constellation. Thus what the physician thought was due to a similar physical constitution the philosopher-astrologer ascribed to the influence and position of the stars at the same time when they were conceived and born. In this case the conclusion of the doctor is much more acceptable, and obviously more credible. For the bodily condition of the parents at the time of copulation could affect the germ cells of the children conceived, so that after the first period of growth in the mother's body they would be born with the same constitution. Thereafter they were nourished on the same food and lived in one home, and in such a case medical science declares that the weather, climate and water supply have much to do with the good or bad predisposition of the body. Accustomed also to the same kinds of exercise, the twins were physically so similar that the same causes sufficed even to bring about the same diseases at the same time. But arbitrarily to drag in the position of the sky and the stars at the time of conception or birth in order to explain the simultaneous sickness, when so many individuals of different races, whose activities and fortunes differed so widely, could have been conceived and born at the same time in one quarter of the earth under one aspect of the celestial sphere, this is a strange piece of arrogance.

Moreover, we have known twins who not only had different occupations and traveled to different places, but also suffered different kinds of sickness. A very easy explanation of this fact, it seems to me, would be given by Hippocrates. He would say that because of differences of food and exercise (matters depending not on bodily constitution, but on the mind's free choice) they might very well experience different states of health. But if we ask Posidonius or any other advocate of the fatal influence of the stars, I should be surprised if he could find anything to say, unless he should choose to dazzle the minds of the ignorant in matters of which they know nothing, but some illusion. They try to make a point of the small interval of time that separates the birth of twins, because of the minute division of the sky where the notation of the hour is placed which they call a “horoscope.” But either this is too small to explain the diversity in will, acts, character and good or bad luck of twins, or else it is too great to allow for the identity of low or high estate in the case of twins. For they account for the greatest differences of this sort solely by considering the hour of birth. Hence, if one twin is born so soon after the other that the horoscope remains the same for each, I demand that everything in their lives should be the same – but such twins can never be found. But if the delayed delivery of the second child changes the horoscope, I demand that they should have different parents, which twins cannot have.

3. Of the argument to meet the problem of twins that Nigidius the astrologer derived from the potter's wheel

It is therefore a futile argument that is offered in the well-known story of the potter's wheel. Nigidius, it is said, when vexed by this question of twins, used the argument in reply, and from it derived his surname of Figulus, or “Potter.” He whirled a potter's wheel with all the force he could, and while it was turning he quickly touched it twice with black ink, supposedly in one place. Then, when the motion stopped, the marks he had made were found to be some distance apart on the edge of the wheel. “Thus,” he says, “given the velocity of the heavenly sphere, even if the second twin were born as quickly after the first as I made my second mark when I touched the wheel, in the broad expanse of heaven it makes a very great difference. Hence arise all the differences that are reported to occur in the character and fortunes of twins.”

The product of his fiction is more fragile than the fictile vases that are fashioned on that rotating wheel. For if a difference in heaven which cannot be measured in the constellations is so important that an inheritance falls to one of the twins and not to the other, how do they dare to deliver to others who are not twins, after observing the position of their stars, statements that depend on a secret that no one can comprehend and set down for the moment of birth? But they may say that such statements are possible in dealing with the horoscopes of those who are not twins because they are based on longer intervals of time, whereas the effects of such minute intervals as may separate the birth of twins affect very small matters about which astrologers are not usually consulted. For who would consult them about when to sit down, when to take a walk, when to eat, or what to eat? But is it really the same thing when we point out that there are very many very great differences in the characters, activities and destinies of twins?

4. Of the twins Esau and Jacob, who were very different in character and actions

To mention a notable case, according to the ancient record of our fathers twin brothers were born so close together that the second was grasping the heel of the first. So great was the diversity in their lives and characters, so great the contrast in their behavior, so great the unlikeness in the love shown them by their parents, that the different in itself made them enemies of each other. Does this imply that while one w as walking the other would be seated, or that one would be sleeping while the other was awake, or one speaking while the other was silent? Such things belong to the minute details that cannot be grasped by those who record the position of the stars under which each man is born, in order that astrologers may be consulted about them. One of the twins was a hired servant, the other was not; one was loved by his mother, the other was not; one lost the birthright, which people then held in great esteem, and the other obtained it. And what shall I say of their wives, their children and their property? How great was the difference! If theses things depend on the brief interval between the birth of twins and are not recorded in horoscopes, why do they mention the same sort of thing when examining the horoscopes of others? But if they mention them because they belong, not to moments too brief to be caught, but to periods of time that can be observed and recorded, then what is the purpose of that potter's wheel? Is it that men with hearts of clay may be set spinning, to ensure that the astrologers shall not be conceived of talking nonsense?

5. How the astrologers are convicted of professing a false science

Now what of those two whose sickness was observed to grow worse, than better, at the same time, a medical observation from which Hippocrates suspected that they were twins? Does not this case sufficiently refute those who would ascribed to the stars what really came from a similar bodily constitution? For why should they grow ill in the same way at the same time, and not first one, then the other, according to the order of their birth, since of course they could not both be born at once? If their being born at different times did not result in sickness at different times, why do they contend that the different time of birth is the cause of difference in other matters? How is it that they could travel at different times, marry, beget children and do much besides at different times, all because they were born at different times, but could not for the same reason grow ill at different times For if the brief delay in time of birth changed the horoscope and caused a different in everything else, why did the sameness which resulted from being conceived at one time persist only so far as periods of illness were concerned? Or if matters of health depend on the moment of conception, while other matters are said to depend on that of birth, they ought not to make a statement about health based on inspection of the horoscope of birth as they do, for the hour of conception is not given them for inspection. But if they foretell periods of illness without inspecting the horoscope of conception, saying that they are indicated by the moment of birth, how cold they tell either of the twins, by considering his hour of birth, when he was going to be sick, seeing that the other also, who did not have the same hour of birth, of necessity had to be sick at the same time?

Now, another question. They say that there is such difference in the time of birth of twins that as a result the aspect of the planets becomes different for them, the horoscopes are different, and hence also all the cardinal points, to which is ascribed such power as to determine differences of destiny. But how could this happen, when it was impossible for them to have different moments of conception? Or if two persons conceived at the same instant of time could have different destinies governing their birth, why could not two born at the same instant also have different destinies governing life and death? The single instant in which both were conceived did not prevent one being born earlier, the other later. Why, then, if two are born at one moment, does anything prevent one dying earlier, the other later? If conception at the same instant still allow twins to have different fortunes in the womb, why does birth at the same instant not allow any two persons on earth to have different fortunes? And that would sweep away all the lies of this science, or rather, of this folly. Why is it that persons conceived at one time, in a single moment, under one and the same aspect of the heavens, have different destinies, which bring them to birth at different hours, and yet two persons similarly born at the same instant under one and the same aspect of the heavens from two mothers cannot have different destinies which conduct them to different fates of life and death?

Or do they not yet have destinies when conceived? Will they not be able to have them unless they are born? Then what do they mean by saying that if the hour of conception could be discovered, they could make statements with better divination? Thus some give currency to the well-known story about the wise man who selected the hour to lie with his wife, in order that he might thereby beget an extraordinary son. And finally, from this same notion comes the reply that Posidonius, the great astrologer and also philosopher, made about the twins who fell ill together. He said that this happened because they were born and were conceived at the same time. Assuredly he included conception in his statement lest someone should point out that it was not clear that they could have been born at the same instant, - thought it was quite certain that they had been conceived at the same instant, - in order that he might ascribe their suffering similar ailments at the same time, not to the obvious cause of similar bodily constitution, but might also make the similarity of their health dependent on the influence of the stars. Then if conception has such power to cause equality of destinies, these destinies should not have been altered by birth. Or, if the destinies of twins are changed because they are born at different times, why should we not rather take it that they were already changed to permit them to be born at different times? Is it possible that the will of the living persons does not change the destinies fixed at birth, while the order of birth does change the destinies fixed at conception?

6. On twins of opposite sex

But in the case of the conception of twins, where both are certainly conceived at the same moment, how does it happen that under the same fatal position of the stars one is conceived a male, the other a female? I know of twins of different sex, both of whom are still living, and still of an age to be active. Although their physical appearance is similar, as far as it can be in opposite sexes, they are nevertheless entirely unlike in plan and purpose of life. In their occupations, of course, there must be a difference between the man's and the woman's. He serves on the staff of a count and is almost always away from his home, while she does not leave her native soil or her own country residence. Besides this there is something more incredible, if you believe in destinies fixed by the stars, but not strange if you consider the free will of man and the gifts of God. He is married, while she is a consecrated virgin; he has begotten a number of children, while she has never even married. But still (they say), the power of the horoscope is very great! I have already shown well enough how truly it is nothing. But whatever be the truth about it, they say that it is effective at the time of birth. Is it also effective at the time of conception? Here it is clear that there is but one act of intercourse, and such is the force of nature that when a woman has conceived, she is entirely unable thereafter to conceive another. Hence the conception of twins must come at the same moment. Perhaps they will say that because they are born with different horoscopes, either he was changed into a male, or she into a female, while they were being born.

It is not entirely absurd to say, with reference only to physical differences, that there are certain sidereal influences. We see that the seasons of the year change with the approach and the receding of the sun. And with the waxing and waning of the moon we see certain kinds of things grow and shrink, such as sea-urchins and oysters, and the marvellous tides of the ocean. But the choices of the will are not subject to the positions of the stars. Accordingly when the astrologers try to make our actions depend on them, it is a warning to us to ask why their reasoning can go wrong even in physical matters. For what is more a part of the body than sex? And yet under the same position of the stars twins of unlike sex can be conceived. Hence what could be more stupid to say or believe than that the position of the stars, identical for both at the hour of conception, could not prevent the sister from having a different sex from her brother with who she shared the same constellation, while believing that the position of the stars at the hour of birth could cause her to differ so widely from him in her life of holy virginity?

7. On the choice of a day for marriage, or for planting or sowing in the field

Now who could tolerate the assumption that in choosing lucky days people manufacture new destinies by their own acts? The man I mentioned, for instance, was not destined by birth to have an extraordinary son, but rather to beget one of no importance. And so, being a wise man, he chose the hour to lie with his wife. Thus he created a destiny that he did not have before, and as a result of his act a thing became fated that was not included in his nativity. What unparalleled foolishness! A day is chosen to marry a wife. I suppose the reason is that unless the day is properly selected an unlucky day might be hit upon and the marriage be unlucky. Then where is the destiny of the stars already decreed when the man was born? Can a man by the choice of a day change the destiny already decreed for him? And then cannot another power change the destiny that he has established by selecting the day? Again if it is only men who are under the influence of the stars, and not everything that lies under heaven, why do they choose certain days as suited to planting vines and trees and grain, and other days for the taming of animals or for letting in the males that are to make herds of mares and cows fertile, and similarly for other matters? But if selected days are important for these matters because the position of the stars, as it varies from moment to moment, has dominion over all earthly bodies and living things, then let them consider what a countless number of things are born, or start, or begin to be at one point of time, and still have such different ends as to convince any child that these observations are absurd. For who is so witless as to make bold to say that all trees, herbs, beasts, serpents, birds, fish and worms have each a different moment of birth? Still, men sometimes do bring to the astrologers to test their skill the horoscopes of dumb animals whose birth they carefully observe at home with a view to this consultation. And they prefer to the rest those astrologers who, after studying the horoscopes, declare that it is not a man, but an animal, that has been born. They even venture to say what sort of animal it is, whether suited for shearing, for riding, for ploughing, or for guarding the house. For they are even tested by inquiry about the destinies of dogs, and their replies are greeted with great shouts of approvals.

Men are so foolish as to think that when a man is born, the birth of all other creatures is delayed so that not even a fly is born simultaneously under the same region of the sky. For if they admit this fly, logic will go on, and step by step small increases in size will lead them to admit the camel and the elephant. Nor are they willing to notice this point: when a day has been selected to sow wheat in the field, many seeds fall on the ground together, germinate together, and as the crop comes up from the ground they become green blades, mature and turn yellow. Yet of this crop some stalks of wheat, that entered the earth and germinated with the others, are destroyed by rust, others devoured by birds and others plucked by men.. How can they say that these were governed by any different pattern of stars, although they clearly have such different ends? Or will they change their minds about choosing days for these things, and say that they are not subject to the decree of heaven? Will they make men alone subject to the stars – men, the only creatures on earth to whom God has granted free wills?

Considering all this, the belief is justified that when astrologers miraculously give true replies, as they often do, this is due to the furtive prompting of evil spirits, whose aim is to plant in the minds of men these harmful beliefs about the control of destiny by the tars, and to confirm them. It is not due to any art of observing and studying the horoscope, for not such art exists.

8. Of those who give the name “Fate,” not to the position of the stars, but to the system of causes that is linked to the will of God

There are some who use the word fate, not of the position of the stars as it is at the time of conception or birth or beginning of a thing, but to the connection and sequence of all the causes whereby everything happens that happens. No great effort need be expended in debate with them on a verbal difference, inasmuch as they ascribe this order and chain, as it were, of causes to the will and power of the supreme God. Most excellently and truly do they believe that he knows all things before they come to pass and leaves nothing disorderly. All powers are derived from him, though the wills of all men are not ruled by him. Thus it is above all simply that will of the supreme God, whose power reaches out with invincible might through the whole universes, that they call fate. This is shown by the following words (the verses, I think, are by Annaeus Seneca) [Epistle 107]:

Lead, O thou Father supreme, of lofty heaven the ruler,

Whithersoever thou wilt, and without delay will I hearken.

Here I am, eager; but should I refuse, then with groans shall I flow;

Vilely shall I endure what I might have performed as a good man.

Led is the willing should by the Fates; they drag the unwilling.

It is quite evident that in this last verse he gives the name of fate to what he had referred to above as the will of the supreme Father. He says that he is ready to obey him, to be led willingly and not dragged unwillingly, for be it noted,

Led is the willing soul by the Fates; they drag the unwilling.

This opinion is also supported by the verses of Homer that Cicero has translated into Latin:

Such are the hearts of men as the brightness of day, that the Father,

Even Jove himself, has dispersed over growth-teeming ploughlands.

On this problem a poet's opinion would have no weight, but Cicero says that the Stoics are accustomed to quote these verses from Homer when asserting the power of fate. So the discussion is not concerned with the opinion of Homer, but with that of these philosophers. These verses, which they employ in the discussion, bring us a clear statement of their view of the nature of fate. They call it Jupiter, who in their belief is the supreme god, and from him, they say, the interconnected links of destiny depend.

De Civitate Dei, V, 1-8, translated by W.M. Green (London: Heinemann and Harvard University Press, 1963), pp. 133-166.