The City of God

it would be condemned to overthrow by the decree of the whole human race. What judgment, then, is left to God concerning the deeds of men, who is Lord both of the stars and of men, when to these deeds a celestial necessity is attributed? Or, if they do not say that the stars, though they have indeed received a certain power from God, who is supreme, determine those things according to their own discretion, but simply that His commands are fulfilled by them instrumentally in the application and enforcing of such necessities, are we thus to think concerning God even what it seemed unworthy that we should think concerning the will of the stars? But, if the stars are said rather to signify these things than to effect them, so that that “position of the stars” is, as it were, a kind of speech predicting, not causing future things⁠—for this has been the opinion of men of no ordinary learning⁠—certainly the mathematicians are not wont so to speak, saying, for example, Mars in such or such a position signifies a homicide, but makes a homicide. But, nevertheless, though we grant that they do not speak as they ought, and that we ought to accept as the proper form of speech that employed by the philosophers in predicting those things which they think they discover in the position of the stars, how comes it that they have never been able to assign any cause why, in the life of twins, in their actions, in the events which befall them, in their professions, arts, honours, and other things pertaining to human life, also in their very death, there is often so great a difference, that, as far as these things are concerned, many entire strangers are more like them than they are like each other, though separated at birth by the smallest interval of time, but at conception generated by the same act of copulation, and at the same moment?

II

On the difference in the health of twins.

Cicero says that the famous physician Hippocrates has left in writing that he had suspected that a certain pair of brothers were twins, from the fact that they both took ill at once, and their disease advanced to its crisis and subsided in the same time in each of them.185 Posidonius the Stoic, who was much given to astrology, used to explain the fact by supposing that they had been born and conceived under the same constellation. In this question the conjecture of the physician is by far more worthy to be accepted, and approaches much nearer to credibility, since, according as the parents were affected in body at the time of copulation, so might the first elements of the foetuses have been affected, so that all that was necessary for their growth and development up till birth having been supplied from the body of the same mother, they might be born with like constitutions. Thereafter, nourished in the same house, on the same kinds of food, where they would have also the same kinds of air, the same locality, the same quality of water⁠—which, according to the testimony of medical science, have a very great influence, good or bad, on the condition of bodily health⁠—and where they would also be accustomed to the same kinds of exercise, they would have bodily constitutions so similar that they would be similarly affected with sickness at the same time and by the same causes. But, to wish to adduce that particular position of the stars which existed at the time when they were born or conceived as the cause of their being simultaneously affected with sickness, manifests the greatest arrogance, when so many beings of most diverse kinds, in the most diverse conditions, and subject to the most diverse events, may have been conceived and born at the same time, and in the same district, lying under the same sky. But we know that twins do not only act differently, and travel to very different places, but that they also suffer from different kinds of sickness; for which Hippocrates would give what is in my opinion the simplest reason, namely, that, through diversity of food and exercise, which arises not from the constitution of the body, but from the inclination of the mind, they may have come to be different from each other in respect of health. Moreover, Posidonius, or any other asserter of the fatal influence of the stars, will have enough to do to find anything to say to this, if he be unwilling to impose upon the minds of the uninstructed in things of which they are ignorant. But, as to what they attempt to make out from that very small interval of time elapsing between the births of twins, on account of that point in the heavens where the mark of the natal hour is placed, and which they call the “horoscope,” it is either disproportionately small to the diversity which is found in the dispositions, actions, habits, and fortunes of twins, or it is disproportionately great when compared with the estate of twins, whether low or high, which is the same for both of them, the cause for whose greatest difference they place, in every case, in the hour on which one is born; and, for this reason, if the one is born so immediately after the other that there is no change in the horoscope, I demand an entire similarity in all that respects them both, which can never be found in the case of any twins. But if the slowness of the birth of the second give time for a change in the horoscope, I demand different parents, which twins can never have.

III

Concerning the arguments which Nigidius the mathematician drew from the potter’s wheel, in the question about the birth of twins.

It is to no purpose, therefore, that that famous fiction about the potter’s wheel is brought