Giordano Bruno's De umbris idearum: Memory, Wheels and Images

In the summer of 1582 a Dominican friar who had fled his convent in Naples published in Paris a book with an enigmatic title, De umbris idearum, “On the Shadows of Ideas”. Giordano Bruno, born in Nola in 1548, had left the order years before and had made a name for himself in France as the master of an extraordinary art of memory. The volume, dedicated to King Henry III, was both a philosophical treatise and a practical tool for ordering the mind.

A Curious King

Bruno himself recounted, years later, before the inquisitors of Venice, how he had caught the king's attention. Henry III had summoned him to find out whether the memory he taught was natural or obtained by magic. Bruno showed him that it was a technique, and the satisfied king granted him an extraordinary paid lectureship.

In the same year Bruno published two more works on memory in Paris: the Cantus Circaeus, in which the sorceress Circe turns men into beasts according to their vices, and a short treatise on the art of Ramon Llull. De umbris appeared together with an Ars memoriae, the most technical part of the system.

Shadows and Light

The title stems from an idea of Platonic origin. Human beings do not see the divine ideas in their pure light, but only as shadows cast in the mind. These shadows, however, are not darkness: they are the way truth becomes accessible to a finite intellect. Working with images therefore means rising, step by step, from the shadows towards the light from which they come.

The ancient art of memory, described in the Rhetorica ad Herennium and by Cicero, placed striking images in well-ordered imaginary places. Bruno transforms it into a system of concentric wheels inspired by Llull's combinations. On each wheel are arranged series of images marked by letters; by turning them, the mind can compose almost infinite combinations.

The Images of the Decans and the Debt to Agrippa

Among the series of figures in De umbris are images of the planets, of the lunar mansions and above all of the thirty-six decans of the zodiac, each covering ten degrees. The historian Frances Yates showed that Bruno took these descriptions from Agrippa's Occult Philosophy, which had in turn gathered them from older astrological sources. The astral figures thus become containers of memory, able to give strength and vividness to recollections.

For Bruno imagination was not a secondary faculty. It was the bridge between the mind and the world soul, and celestial images served to attune one to the other. In this sense the art of memory came close to Ficino's natural magic, while remaining a mental discipline rather than a rite.

De umbris idearum opened the most productive period of Bruno's life; after Paris he moved to England, where he wrote his great Italian dialogues. The book shows how, by the end of the sixteenth century, Agrippa's legacy had entered the thought of the most original philosophers, transformed into an instrument of knowledge.