Girolamo Cardano: Physician, Mathematician, Astrologer and Man of Fate

Few figures of the sixteenth century left so candid a portrait of themselves as Girolamo Cardano. Born in Pavia in 1501, the illegitimate son of the Milanese jurist and mathematician Fazio Cardano, he was a physician of European fame, a leading mathematician, a natural philosopher and an astrologer. In his last years he wrote an autobiography, De vita propria, in which he frankly recounts successes, misfortunes, vices and convictions, including those about the occult world.

The Mathematician of the Ars magna

In 1545 Cardano published in Nuremberg the Ars magna, a treatise on algebra that contained for the first time in print the general solutions of cubic and quartic equations. The solution of the cubic had been confided to him by Niccolò Tartaglia, who accused him of breaking an oath of secrecy, and the dispute that followed has remained famous. Cardano also wrote a short treatise on games of chance, among the first studies of probability.

This mathematical skill coexisted without contradiction with astrology. For Renaissance men astrology was a science of the heavens requiring precise calculation, and Cardano was one of its leading practitioners. He published collections of genitures, that is, birth charts of famous people, and an extensive commentary on Ptolemy's Tetrabiblos, the fundamental astrological handbook of antiquity.

Subtleties and Varieties of Nature

His most widely read works of natural philosophy were De subtilitate, of 1550, and De rerum varietate, of 1557. They are vast encyclopaedias dealing with mechanics, metals, animals, dreams, prodigies and demons. Among other things Cardano describes a suspension system for keeping an object level, which still bears his name, and a method of hiding a message within a text by means of a perforated grille.

On occult phenomena his position wavers. He often seeks natural causes for what common people attributed to magic, yet he admits the existence of spirits and recounts unusual personal experiences. In De vita propria he states that throughout his life he enjoyed the protection of a guardian spirit, as his father Fazio had before him, who according to family accounts had for years kept company with a familiar demon.

The Horoscope of Christ and the Arrest

In his 1554 commentary on Ptolemy Cardano included a horoscope of Jesus Christ, interpreting his life in the light of celestial configurations. The idea was not entirely new, but to many it seemed a dangerous subjection of the Son of God to the stars. In October 1570, while teaching medicine in Bologna, Cardano was arrested by the Inquisition and held for several months.

After his release he was forbidden to teach and publish, but he moved to Rome, where Pope Gregory XIII granted him a pension. He died there in September 1576. A rumour, already current among his contemporaries, held that he had foretold the date of his own death and let himself die so as not to disprove the prediction: it is an anecdote, not a documented fact.

Cardano represents a human type typical of the Renaissance, in which the utmost mathematical precision and faith in celestial influences meet in the same mind. His autobiography, printed only in 1643, remains one of the liveliest documents for understanding how a sixteenth-century scholar experienced his relationship with fate and the invisible.