The Scientific Revolution in Astrology: The English Reformers, 1558-1686

Astrology was once an integral part of the scientific enterprise. By the end of the seventeenth century it had sunk to the level of pseudo-science in the eyes of virtually all learned men. Some historians have thought that the belief in astrology was undermined by scientific advances, especially in astronomy. Others have argued that its demise can be explained by the change in the concept of man's place in the universe, that is, the championing of human free will and the rejection of celestial determinism. In contrast to previous historians, I have paid most attention to astrological texts, concentrating on English astrology from 1558 to 1686. From this perspective, the decline of astrology takes on the appearance of the failure of a scientific revolution. In a prologue I set forth the intellecutal background for a scientific revolution in astrology; a selection of the principles and rules of traditional astrology for the most part according to Claudius Ptolemy (2nd c. A.D.) and a sketch of the arguments against astrology given by Giovanni Pico della Mirandola (15th c.). I also point out how calculations differed under the Ptolemaic, Copernican, and Tychonic cosmological systems. Then I investigate the social setting, mostly by examing the relationships between astrologers and astronomers in Tudor and Stuart England. Through the first quarter of the seventeenth century, with a few exceptions, English astrologers were the same men who were engaged in the successful revolution in astronomy. Later, the leaders of English astronomy were in general no longer involved in astrology, but competent astronomers of the next rank were still practicing astrologers. In the rest of the dissertation I examine several efforts to make astrology into a modern science, including the work of a few continental astrologers. I treat the astrologies of John Dee, Jofrancus Offusius, Johannes Kepler, Christopher Heydon, Robert Fludd, Francis Bacon, Joshua Childrey, John Goad, Claude Gadrois, Robert Boyle, and Richard Mead. The reformers agreed with Pico that they recognized that astrology as it was then practiced was faulty. Pico has already been assigned a role of great importance in late astrology by historians who emphasize his stand on self-determination. In the context of reform, however, his most important contribution was his detailed criticism of the principles and rules of astrology. The men attempted to construct new astrologies had different perceptions of how reform should be approached. There were among them Neoplatonists, Aristotelians, and Mechanists. I have also considered one Newtonian who was interested in understanding celestial influences. Great ingenuity was exercised in drawing up these astrologies, each of which in its day would have been regarded by at least some scientists as an entirely appropriate means of understanding nature. In general, heliocentrism and the observations which indicated the mutability of the heavens were not seen by the reformers as threats to astrology. Often, in fact, they thought that these discoveries provided a better grounding for astrology. The new astrologies were not supposed to be merely plausible, but empirical evidence was used, or its use was advocated, to develop and test them. In a few cases it has been possible to examine the interaction of theory and observation. On the whole, bad methods did not cause the failure of this revolution; the reformers were simply attacking a problem that could not be solved.