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Claudius Ptolemy and Vettius Valens both studied the art of astrology around 200 CE. Though contemporaries, there are nuances to the ways the two men present their understandings of astrology. A close reading of their descriptions of the planets points to a few key differences in their views of the solar system resulting from their individual conceptual references. Analyzing the different ways in which two of the leading figures of the time understood astrology suggests that there were competing views of astrology, despite the fact that the discipline was historically quite young at this time. This diversity of views regarding the planets may show that knowledge was transmitted and assimilated in a variety of ways, supporting a number of astrologies in contrast to one universally accepted practice.

In addition to presenting a wealth of astrological information, Book I of the Tetrabiblos contains Ptolemy’s exposition of the planets. Each body is briefly treated with a paragraph explaining the nature of the planet in terms of the four temperamental qualities: hot, cold, wet and dry. Mars, for instance is described as having “a nature chiefly to dry and to burn” (Ptolemy 14). The Greek school of thought that described the natural world in terms of its 4-fold elemental composition was first examined in Empedocles’ 4 “root” theory around 450 BCE, hundreds of years before Ptolemy’s work. Plato would later take up Empedocles’ theory and explain the roots as four elements which make all structures in the world (Empedocles). Hippocrates, often called the father of medicine, would eventually codify this theory into one of the first systematic schools of medicine (Humorism). This is a tradition of thought that began long before Ptolemy and continued to develop in the Western history of philosophy. Ptolemy’s astrology is closely aligned, therefore, with the prevailing views of science at the time.

This classification of planets and signs according to their temperamental qualities would become a foundation of Medieval and Classical astrology and medicine. The notion of humor and temperament as indicators of personality grows directly from this lineage. In fact, many of Lilly’s techniques rely upon information derived directly from Ptolemy’s texts (Lehman 38).

Valens’ discussion of the planets is much more colorful. In The Anthology, Book 1, Valens describes the planets in a number of ways. In his treatment, the planets are anthropomorphized to match their Greek mythological namesakes. “Aphrodite is desire and love,” for instance (Valens 4). Additionally, each planet is often associated with a list of professions, activities and events, grounding the description of the planet in the practical and social reality of the time. Holden writes that Valens operated a school of astrology (Holden 49), so it may be feasible that Valens had more experience presenting this material and adopted a more illustrative approach in order to communicate more effectively. In addition to contextualizing each planet in the reality of everyday life, Valens provides a number of planetary rulerships for each body. Planets are given rulership over anatomical parts of the body, metals and stones, personality characteristics and fates in life. In Valens’ treatment of the planets, the reader encounters a symbolic language, not unlike contemporary astrology keywords.

Valens also mas a more direct engagement with the concept of fate in his writing. The Anthology has a more poetic and lyrical tone than scientific demeanor of Ptolemy’s Tetrabiblos. It seems to bear more resemblance to the verse presentation of the Astronomica by Manilius. Where Ptolemy’s understanding of the planets fits in nicely with an already existing school of philosophy, Valens presents a more esoteric and symbolic perspective. In the conclusion to his treatment of the planets, he references the three types of fate described in the Corpus Hermeticum: tyche (choice), pronoia (providence), and ananke (necessity). The Corpus Hermeticum, a collection of wisdom texts from the second and third centuries CE, has a strong Egyptian influence and is contemporary to both Ptolemy and Valens. Hermes Trismegistus, the deity to whom the texts are attributed is a fusion of Greek and Egyptian mythological figures (Hermetica). It’s quite likely that Valens is introducing a strain of this tradition into the more formal astrology that is espoused by Ptolemy at the time. This may suggest a more diffuse spread of astrological knowledge throughout the same land.

It’s striking that two experts in such a small field could have such diverse understandings of the planetary underpinnings. Where Valens seems to incorporate esoteric and metaphysical teachings into his astrology, Ptolemy describes a science that is in direct alignment with the contemporary Greek school of thought. At this point in history, there is a great deal of information moving with the Mediterranean trade routes of the time. Communications are moving between Egypt, the Middle East, the Hellenistic world and India, not to mention all the work being translated. While each astrologer appears to be loyal to an intellectual tradition — Aristotelianism for Ptolemy and Esotericism for Valens — it appears that each astrologer also may have integrated texts from sources that were outside their native culture.


  • Empedocles. Wikipedia.
  • Hermetica. Wikipedia.
  • Humorism. Wikipedia.
  • Holden, James Herschel. A History of Horoscopic Astrology. American Federation of Astrologers: 1996.
  • Lehman, Ph.D., Dr. J. Lee. Classical Astrology for Modern Living. Whitford Press: 1996.
  • Ptolemy, Claudius. Tetrabiblos, Book I. Robert Schmidt, trans. Project Hindsight: Greek Track Vol. 5: 1994.
  • Valens, Vettius. The Anthology, Book I. Robert Schmidt, trans. Project Hindsight: Greek Track Vol. 4: 1993.
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