The Commentaries on the First Aphorism of the Pseudo-Ptolemaic Centiloquium

Am 6. Juni 2014 habe ich einen kurzen Vortrag auf der ‘Conference on Astrology and Anti-Astrology in the Renaissance‘ an der University of Warwick gehalten. Es folgt hier eine leicht gekürzte und überarbeitete Fassung:

In this paper I wish to discuss a problem I also discuss in my dissertation which hopefully will be published in 2015. In this dissertation I created a complete list of astrological textbooks and ephemerides in Latin published until 1610. Furthermore I discuss the contemporary prefaces and commentaries of these textbooks in which is explained what astrology is and how it should work. In this matter I focus on the problem in which way astrology should be a science, and I also discuss how astrology is different from theology or magic.

Now I want to discuss a small but in my opinion very important topic of my dissertation. This is the difference of particular and general predictions according to the Ptolemaic sources. The main sources are the Tetrabiblos (Quadripartitum in Latin) and the pseudo-ptolemaic Centiloquium. I want to start with the Centiloquium.


The Centiloquium was printed as appendix to the Tetrabiblos or as a singular print with commentary. Altogether it was printed 27 times which means that it is the most printed astrological work in Early Modern Europe. The first prints base on a medieval translation and contain a commentary which was ascribed to the Arabic author Haly Ibn Ridwan. Newer printings often use the translation of the Italian humanist Giovanni Pontano who translated the Centiloquium from a Greec version and wrote an extensive commentary. The commentary was written in the years 1477 and 1490 and was posthumously printed in 1512. A further translation and commentary was created by the Greek scholar George of Trebizond in the 15th century. This commentary was firstly printed in 1540.

Now we know very well that the Centiloquium couldn’t be created by Ptolemy himself. The first time a scholar doubted this was in 1554. It was Girolamo Cardano who mentioned some big differences between the Centiloquium and the Tetrabiblos which let him know that the Centiloquium couldn’t be of Ptolemy. Cardanos opinion was good known by the scholars of the late 16. century but the printers of the Centiloquium often ignore this fact and it was still popular.

The Centiloquium contains one hundred aphorisms which deal mainly with practical notes on the interpretation of special constellations or astrological theories. Some aphorisms are more general. They admonish that astrological prognoses should be made carefully and rational. Someone who wants to predict the future should be aware of the doctrine of the nature. He should be a wise man, and he shouldn’t be controlled by his own affects. In the fifth aphorism the author says that the astrologer can avoid future events if he know the celestial influences properly.

Of special importance is the first aphorism. The author discusses here different kinds of astrological predictions. But there are different versions of this aphorism. If you look into the Arabic version, the text is longer and seems to transport more information: You can read the following:

The science of the stars is of you and of them. But the astrologer mustn’t predict something special but rather universal, like he sees something from afar. Therefore someone acts who considers a thing according to his matter and doesn’t get a certain cognition about this. We have about a thing a dubious cognition from the matter, but from the form a certain. And these judgments, I teach you, are in the middle of necessity and possibility. I said you that these judgments are between necessity and possibility because this is with him who considers the natures of the things and the opus of the stars. But those having a cognition from the better part of the soul are close to the truth about the future because the power of the soul dominates in them, although they haven’t very much science of this art. Ptolemäus et al. (1493), fol. 107ra

I want to focus on the fact, that this aphorism refers to the dualism of matter and form which was commonly used in the Aristotelian tradition. According to this, only universal (universalis) predictions can be made because they depend on the form. In contrast, special (specialis) predictions shouldn’t be made because they are connected with matter from which you cannot have a certain cognition.

The only commentary to this aphorism, which was printed in Early Modern Europe, was of Haly Ibn Ridwan. He explains the twofold discrimation “of you and of them” and identifies “them” with the movements of the stars. You can make predictions in this way insofar you interpret the signs of the stars with the traditional astrological writings. In the last section of the aphorism, Ptolemy seems to speak about a different kind of prophecy. He mentions humans who possess a “better part of the soul”. Haly writes that these humans are able to separate themselves from everything mundane like the hermits. They are free from corporal guilty and gain the cognition of the future with huge excitement. According to this, the last kind of predictions doesn’t depend on astrological forecasting because it is reached from the human soul itself connected with the divine spirit.

But the first aphorism in the newer translation from the Greec is quite different. You can read in the translation of Pontano the following (I omit the translation of George of Trepizond because it’s quite the same):

From you and from the science. It can’t happen that someone, who is wise, declares the particular forms of the things, such as the sensation doesn’t receive a particular but rather a certain general form of the sensual thing. And it should be that he, who exerts this, uses a conjecture of these things. Only they who are inspired by the numen predict particular things. Pontano & Ptolemäus (1519), fol. 2v

There are some differences to the older translation from the Arabic. The dualism of form and matter disappeared. In contrast, the argumentation bases more on perception. The middle section in which you can read that judgments are in the middle of possibility and necessity also disappeared. However, the contents of both seems to be that only general or universal predictions can be made from the stars.

Indeed, the terminology is not clear. The medieval translation uses the words universalis and specialis. The newer translations uses generalis and particularis. Pontano explains in his commentary that these things, which are called individuum, also count to particular entities.


We must consider that we have a further source of these concepts: the Ptolemaic Tetrabiblos which was the most famous astrological textbook in Early Modern Europe. It was printed 18 times in a Latin version. Ptolemy himself uses this difference at the beginning of the second book. He says that the general effects of the stars are prior to the particular effects. Therefore it could happen that some particular effects can’t take place because the general effects avoid them. For example, if there is a good constellation of the stars in a birth chart, this can be prevented by a war which belongs to the general influences of the stars.

Ptolemy divides his Tetrabiblos in this way. The second book belongs to general predictions and contains weather forecasting and influences on regions. The third and fourth book belong to particular predictions and deal with natal astrology.

But this seems to be a contradiction to the Centiloquium because Ptolemy deals in the Tetrabiblos with particular predictions as well which shouldn’t be done according to the first aphorism of the Centiloquium.


George of Trepizond tries to solve this problem in his commentary to the first aphorism. There, he differs between three kinds of predictions. The first belongs to scientific predictions which are general predictions. The second belongs to particular predictions which are not scientific but could be done with prudence (prudentia) and conjecture (coniectura). The third kind is not an astrological prediction. Like the explanation of Haly, it belongs to divine inspiration. With the help of the divine numen you are also able to do particular predictions.

This argumentation about the first two kinds of predictions is very similar to the explanations you can find in the Nicomachean Ethics of Aristotle. In book VI, Aristotle defines prudence as a consideration about good or bad actions. Therefore, if you consider your actions, you have to respect particular circumstances which cannot be foreseen by a science. Science only deals with universals. According to Aristotle, prudence is also distinguished from wisdom because wisdom bases on science and rationality.

You can find the same argumentation in the writings of Giovanni Pontano. If you look in his commentary to the first aphorism, he uses a quit broader argumentation about predictions and doesn’t make such clear distinctions. But you can find the same argumentation in his writing De prudentia which he wrote in 1499. Pontano argues here that human actions belongs to prudence and deals with particularities. In contrast, science is based on demonstrations, and scientific knowledge is certain and necessary. It uses universals and doesn’t deal with singular and particular things.


If we consider the influence in the 16th century, which I also discuss in my dissertation, we can see that this distinction in general and particular predictions is used in different vocabularies. So you can find sources which differ into special and universal prognoses, other differ into particular and general prognoses.

It also isn’t possibly to identify particular prognoses with natal astrology. For example, in textbooks of Francesco Giuntini or David Origanus natal astrology itself is divided into two parts which contain either general or particular predictions.

But they all agree that particular predictions only mean certain predictions about future events especially of human beings. The authors refer mostly to the human free will to declare that no future event of humans can be foreseen by the stars for certain. But if you only consider the mixture of the elements, you are able to do very confident predictions from the stars and you can also foresee the changes of the human temperaments.

To summarize this shortly: In this Aristotelian tradition, the astrologer is not able to do scientific prognoses about particular things or events in the future. But if you want to forecast particular things, you can use conjectures and prudence.

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