Amongst the books on traditional astrology that I came across, Ptolemy's "Tetrabiblos" was one of the more enlightening. We know Ptolemy through his reputation as the writer of the "Almagest" or "Great Treatise" on astronomy. The "Tetrabiblos" was his treatise on astrology. Reading the Tetrabiblos came as something of a surprise because I had assumed that, owing to the age of the book (written in the 2nd Century AD), I would be unable to relate to the contents, or that it would be versed in a language that was unreadable. While it is true that a few passages are demanding, the book as a whole is quite well structured and coherent.
It is interesting to note that astrology was 'traditional' even as Ptolemy sat down to write about it. His treatment of the zodiacal signs "as they have been handed down by tradition," meant he was passing on second-hand rather than directly perceived knowledge. And yet in spite of this, he manages to treat his subject matter with a degree of understanding that is somehow lacking in some of the more modern commentators.
Ptolemy is in no respects in thrall to the ancients: he provides the reasons underlying the choice of attributes given to each of the planets, signs, aspects and so on, and comments favourably or unfavourably as he sees fit. His exposition also contains echoes of the empiricism that once lay at the foundations of astrology. For example, he describes the planets and the fixed stars in terms of the Aristotelian principles of hot, cold, wet and dry:
"The nature of Mars is to dry and to burn, in conformity with his fiery colour and by reason of his nearness to the sun..."
After outlining the nature of each of the planets in this way, he then goes on to base the more familiar astrological classifications ('beneficent and maleficent', 'diurnal and nocturnal' 'exaltation and depression' etc) on the same four principles. The seasons and their relationship to the zodiac are treated in the same manner:
"Aries is the starting point of them all, making the excessive moisture of the spring the first part of the zodiac..."
The great advantage of this approach is that, in providing the underlying principles, the reader can consider directly what if any validity there is in them.
In addition to the 'principles', the Tetrabiblos also provides some insight into the origin of the aspects. For example, the equilateral triangle was regarded by Platonic philosophy as the "most elementary plane figure" (Timaeus, 22). Ptolemy describes it as "most harmonious with itself". It is for this reason that 'trine' is regarded as beneficial. Once again, being provided with the origin and reason for the choice, the reader can think their way into the concept and decide what, if any, validity there is behind the statement.
Book I provides the outline of astrology as a whole. Book II deals with 'general' astrology, or with the destiny of countries, ages, peoples, events and so on. Ptolemy outlines, in quite an even-handed manner, a description of the nature of the different races populating the different parts of the earth. This can, it must be said, be inadvertently humorous. For example, his depiction of the British, Germans and Italians:
"...they are without passion for women and look down on the pleasures of love, but are better satisfied with and more desirous of association with men."
Books III and IV deal with 'genethliacal' astrology, or that which pertains to the individual. It must be said that, after the initial coherent reasoning of Book I, the later books tend towards long lists of calculating the aspects and much accumulation of detail.
It is intriguing to note that Ptolemy has very little to say about the psychological qualities of the planets and the fixed stars. His method is either empirical, describing the planets in terms of the qualities, or deductive, based on his calculations of the aspects or relationships between the planets. The translator of the Harvard University Press version, F. E. Robbins, describes him as a "scientific astrologer". I think this is an appropriate term, and gives some indication of his treatment of the subject. Ptolemy clearly sought to present, at all times, an objective assessment of the subject. The method employed in the Tetrabiblos is the natural outcome of the way astrology came to be treated once human beings were no longer able to have direct experience of the spiritual nature of the planets.
The Tetrabiblos is worth having for anyone interested in understanding traditional astrology and its development. It is quite likely that the outline and content of the Tetrabiblos provided the template for much of the astrological writing that came later.