To be fair to Fagan, this wasn?t just a ?theory?. He conducted extensive research into this and it was pretty much part of his life-work. He wrote about it in his book
Zodiacs Old and New. Or you can find it described in Rupert Gleadow?s work
Origin of the Zodiac.
Before this there had been a lot of speculation about whether the exaltation positions represented a horoscope of some great event or a great person. But as Sue says, because of Mercury?s position it?s clear this cannot be the chart of one moment in time.
The most important planetary phenomena of ancient astrology were heliacal risings and settings. After studying all the planetary data for the period Fagan concluded that the exaltations were based upon celestial events of 786 BC - because all the planets had heliacal phenomenon in or near their exaltation degrees in that year. He then researched to discover if there was anything special about that year and discovered that it was in this year at Calah or Kalakh (Khaldea, Chaldean), that a temple was dedicated to Nabu (patron god of astrologers) upon which was inscribed
Thou who shalt follow after, trust not in any other god.
Fagan?s argument is not that they were offering a new ?Horoscope of the Universe?, but, being impressed by those ideas and wanting to compete with them, they decided to establish their own great year of importance - one in which their knowledge in astrology became spectacularly enhanced. It was only around this time that the tropical zodiac began to emerge and we start to see a great development of astrology after this period.
We know the exaltation positions are Mesopotamia in origin. Ptolemy, in his
Tetrabiblos, did not list the specific degrees. He attempted to explain why each planet was allocated to its associated sign according to an agreement of nature or because of a specific relationship with the Sun. The Sun is exalted in Aries because in this sign the Sun makes its transition to the northern hemisphere and its power increases. The Moon receives her exaltation in Taurus because after her conjunction with the Sun in Aries (the New Year syzygy), she first appears and begins to increase her light in this sign. In his explanation of the Sun and Moon, Ptolemy is very close to making the same point as Fagan ? that they represent the Sun?s return to the vernal equinox in spring, and the Moon?s first appearance after that event which was important in New Year (ie, spring) festivities, just as the Moon is important in setting the date of Easter today.
Beyond that Ptolemy?s explanation relies upon aligning planets with places that demonstrate their association with winds or humours. For example, Jupiter is assigned to Cancer because it has a particular affinity with the direction north and rules the northerly wind. In Cancer Jupiter reaches its furthest zodiacal position north and therefore comes to the fullness of its power. Venus is moist by nature and so receives her exaltation in Pisces, where the beginning of the moist Spring is indicated.
Porphyry, who wrote a commentary on Ptolemy, offers a further suggestion: the diurnal planets are exalted according to their trines and the nocturnal ones according to their sextiles, since the latter have weaker rays. For example, the Sun, in ruling Leo, has an exaltation in Aries, on the trine of Leo, but the Moon has its exaltation in Taurus, on the sextile of Cancer. However, the rule does not hold true for Mercury which, exalted in its own sign of Virgo, makes a square aspect to its other sign of rulership in Gemini.
I also remember that David McCann wrote an article about the exaltaions in the AA Journal some years back and he may have had some additional thoughts. But I only have a vague recollection of considering the article important and worth revisiting ? at the moment those journals are packed in the loft where it?s not easy to get to them.
I don?t think that any of the attempts to rationalize the positions have been fully satisfying - for this issue it may be very constructive to think ?outside the square? like Fagan did.
Getting back to the original post, I have been asked to point out that Maurice McCann?s book
The Sun & The Aspects explains how Ptolemy decided on the rulerships, exaltations etc. He deals with rulerships in chapter 3, 'Who Rules What and Why?' and in chapter 4, 'Essential Dignities? and offers some information on the 'Terms' in the Appendix. I haven?t seen this book myself but the blurb looks very interesting. Details are on Maurice McCann?s website at
http://www.tara-astrology.com