A History of Western Astrology – S. J. Tester – Boydell Press (1987)

What the Book Explores

In A History of Western Astrology, S. J. Tester provides a comprehensive chronological survey of the development of astrological thought in the Western world. Rather than approaching the subject from the perspective of a believer or a skeptic, Tester examines astrology as a significant intellectual and cultural phenomenon that occupied a central place in Western history for over two millennia. The work traces the evolution of these ideas from their formative stages in the Hellenistic period through their dominance in the Middle Ages and the Renaissance, finally documenting their eventual marginalization during the Enlightenment.

One of the primary themes explored by Tester is the technical and mathematical sophistication of the astrological tradition. He details how the Greeks transformed the omen-based observations of the Babylonians into a rigorous geometric and philosophical system. The work highlights the contribution of figures like Ptolemy, whose Tetrabiblos sought to provide a naturalistic, Aristotelian foundation for the influence of the heavens on Earth. Tester explains that for much of history, astrology was not viewed as a ‘fringe’ belief but as a legitimate branch of natural philosophy—a precursor to what we now distinguish as astronomy and physics.

The book also examines the internal logic of various astrological systems. Tester discusses the development of house systems, the importance of planetary aspects, and the intricate calculations required to cast a nativity. By focusing on these technical aspects, the author demonstrates that astrology was an academic discipline requiring significant education and literacy. This contextualization is essential for understanding why astrology was taught in universities and patronized by both the clergy and the crown for centuries.

Historical / Cultural Context

Published in the late 1980s, S. J. Tester’s work represents a period in historiography where scholars began to take the ‘rejected’ sciences—such as alchemy and astrology—seriously as subjects of historical study. Before this shift, many historians of science treated astrology as a mere aberration or a lingering superstition. Tester, however, treats it as a vital component of the Western intellectual lineage, essential for understanding the history of medicine, mathematics, and philosophy.

The work is particularly notable for its exploration of the tension between astrology and religious doctrine. Tester chronicles the long-standing debate within the Christian Church regarding celestial influence. He notes the transition from St. Augustine’s early rejection of the practice—based on concerns regarding human free will—to the later medieval synthesis, where theologians like Thomas Aquinas allowed for the idea that ‘the stars incline, but do not compel.’ This historical nuance reveals how astrology adapted to survive within different ideological frameworks.

The book concludes with a discussion of the ‘death’ of astrology in the 17th and 18th centuries. Tester argues that it was not merely the rise of the telescope or the Copernican model that rendered astrology obsolete in academic circles. Instead, it was a fundamental shift in the philosophical understanding of the universe. As the world moved toward a mechanical worldview, the ancient concept of a ‘living’ cosmos, where the celestial and terrestrial were linked by symbolic correspondences, began to lose its intellectual coherence.

Who This Book Is For

This work is intended for readers who seek a rigorous, academic account of how human beings have historically interpreted the heavens. It is particularly well-suited for students of the history of science and the history of ideas who want to understand the lineage of Western cosmology without the sensationalism often found in contemporary astrological literature.

Those interested in the development of Western philosophy will find Tester’s analysis of the interaction between Greek thought and celestial observation illuminating. Similarly, readers with a background in medieval or Renaissance studies will benefit from the book’s explanation of how astrology informed the cultural and political life of those eras. It is not a guide to practicing astrology, but rather a guide to understanding its role as a structural element of Western civilization.