As I conclude my labors on a new translation of the Liber aggregationis, or Book of the Gathering, ascribed to Albertus Magnus—also known as The Book of Secrets of Albertus Magnus—I have been reviewing noted authors who studied it. One of these is Giordano Bruno, who was infamously executed by the Roman Inquisition for heresy in 1600. Among his extant writings on magic is the De magia mathematica, which contains the following seventeen canons derived from the former work.  (For ease of reading, Bruno’s references to page numbers have been dropped. The “science” of which he speaks is the science of magic.)

The General Doctrine of Albertus

Leaving aside those matters which have to do with the enigmas of practice, the chiefest and most approved things in this science—of which there are many—must be collected from the pre-eminent Albertus.

I. The first of these is that this science is good—on the authority of the Philosopher, who affirms every science to be of the genus of good things—and that if there be just complaints on account of it, these do not proceed from the science itself, etc.

II. Concerning the method of working, as he says, a good effect looks to a good planet, but an evil effect to an evil one—that is, to their hours and days.

III. On the seven chosen herbs possessing the influence of the seven planets, etc. The first of these, which is called Asphodel, is of Saturn.

IV. On the virtues of stones. The first of these is the Magnet, etc.

V. On the virtues of animals. Some of these he adduces as though by augmentation, etc.

VI. On the times and rulership of the planets and stars, of which above.

VII. On the effects pertaining to each of the planets. For he says that life is under Saturn, etc.

VIII. That those things which are seen in characters, enchantments, sorceries and speeches, as well as many very base things, which seem wholly impossible and without a sufficient cause, are not therefore to be despised.

IX. That in the souls of men there is a virtue of altering things, etc. From this it is plain that not all who know the theory and grasp the reason of this art can make the proper use of it, such as is wont to be found among the uneducated and foolish, who grasp little or none of the reason for its virtue and efficacy.

X. That the hours are to be observed, etc.

XI. That the art of making characters is one possessing efficacy from the mind which strives with a great desire, etc.

XII. That it must be known concerning things, that all incline towards themselves through their species and forms, etc.

XIII. That it has been said concerning the attraction and inclination of all like things to like, etc.

XIV. That every thing is full of marvelousness, etc.

XV. That the pure astrologer is not to be believed in referring all marvelousness to the heavens, etc.

XVI. That marvelousness can come forth from things in divers ways, and through the celestial virtues, etc.

XVII. That it must be noted concerning things that they are of what qualities, dispositions and properties, etc.