This mixture of anatomical and chiromantic terminology is characteristic of its author. Girolamo Cardano was a brilliant and flamboyant character, his life a melodrama of poor health, a troubled career, and family disasters, all compounded by political and religious instability. Analytical, eccentric, and supremely sure of himself, Cardano, at the end of his life, wrote a bizarre but still entertaining autobiography. Contemporaries admired his achievements in mathematics, medicine, and natural philosophy, all of them blended with astrology, natural magic, and divination. In 1560 the Inquisition accused Cardano of heresy; casting Christ's horoscope was especially imprudent. Cardano wrote more than two hundred works. The book in which the chiromantic diagram appears is a supplement to the first of two encyclopedic projects, De subtilitate libri XXI, published in 1550. Both his encyclopedias enjoyed great contemporary popularity and range widely in subject matter, including cosmology, mechanics, the natural sciences, technology, cryptology, and the occult sciences. Cardano's extensive treatment of chiromancy in chapter 79 of the De rerum varietate begins with an enumeration of the parts of the hand, viewed as an instrument of the body and a book of the soul (p. 557). He discusses the influences of the planets, as well as the numbers, names, and significance of marks on the hand, its lines, spots, colors, and creases. His autobiography tells us that he saw his own destiny in the lines of his own hand, yet the same work distances him from the form of divination that became riskier as the century wore on.
The above is slightly adapted from a catalogue entry by Brian P. Copenhaver and Claire Richter Sherman, in Claire Richter Sherman, Writing on Hands: Memory and Knowledge in Early Modern Europe (University of Washington Press for The Trout Gallery at Dickinson College, 2000).
Nancy G. Siraisi, The Clock and the Mirror: Girolamo Cardano and Renaissance Medicine (Princeton: Princeton University Press, 1997)
Anthony Grafton, Cardano's Cosmos: The Worlds and Works of a Renaissance Astrologer (Cambridge, Mass.: Harvard University Press, 2000).
Girolamo Cardano, The Book of My Life (De vita propria liber), trans. Jean Stoner (New York: E. P. Dutton, 1930).