Girolamo Cardano and the Tradition of Classical Astrology The Rothschild Lecture, 1995 ANTHONY GRAFTON DodgeProfessor of History, Princeton University I. CONTINUITIES OF IDEOLOGY AND TECHNIQUE or two anda half millennia, astrologers havescrutinized the skies in order to predict the careers of individuals, the results of commercial ventures, the fortunesof individual countries, andthe history of the entire world. The oldest surviving individual horoscopes are the work of Mesopotamian astrologers, prepared in the fifth century B.C., and after 1 The most recent ones that could still claim scientificstatuswere drawn up by some of the most technically advanced natural philosophers in seventeenth-century Rome and London.2 No modern university has a department of astrology, but it still flourishes acrossthe western world, in elegant occult bookshops from Geneva to Pasadena as well as in supermarkets and the back pages of tabloid newspapers. To judge from the expensive cars that regularly park outside the house of one of my neighbors, an astrologer who did pioneering work on the development of computer programs for rapid andaccurate composition of horoscopes, members of the modern social and intellectual elitestillfindthis ancient artof considerable interest. Any historian who attempts to study an individual segment of this long history must repeatedly risk mistaking traditional, and even ancient, ideasandmethods for new ones.For the historian of classical astrology confronts a tradition that lasted many centuries, one that combined On the origins of astrology see the classic study of A. Sachs, "Babylonian Horoscopes," Journal of Cuneiform Studies 6 (1952), 49-75, and the more recent work ofF. Rochberg- Halton,e.g. "New Evidencefor the History of Astrology," Journal of Near Eastern Studies 43 (1984): 115-40 and "Babylonian Horoscopes and their Sources," Orientalia 58 (1989): 102-23. For surveys of the history of astrology in the ancient world, see S. J. Tester, A History of Western Astrology (Woodbridge, 1987), and T. Barton, Ancient Astrology (London andNew York, 1994), which have the merit of existing even if they do not fill all needs. 2 See respectively G. Ernst, Religione,ragione e natura (Milan, 1991), chaps. 10-11, and P. Curry, Prophecy and Power (Princeton, 1989). PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY, VOL. 142, NO. 3, SEPTEMBER, 1998 323