North, J. D., 1989, Stars, Minds and Fate: Essays in Ancient and Medieval Cosmology, 63-4.
Abu Ma'shar's work on conjunctions seems to have been much influenced by his teacher al-Kindi, the first great philosopher to have written in the Greek tradition in Arabic. Al-Kindi firmly believed that knowledge through revelation and prophecy is superior to the truths of unaided reason. He wrote on astrology, and, in a letter which is still extant, attempted to predict the duration of the empire of the Arabs on the basis of planetary conjunctions. Broadly speaking, the rarer the conjunction affecting political and religious events, the more potent its force. This is the doctrine central to my survey, and al-Kindi's editor, O. Loth, thought it began with him.
In order of the slowness with which they traverse the zodiac, Saturn comes first (29.5 years), followed by Jupiter (11.9 years) and then Mars (1.88 years). Roughly speaking, Saturn and Jupiter meet every twenty years, while Mars meets with Jupiter about every two years and with Saturn marginally more often. Although it is impossible to be very precise without being inordinately tedious, we can say that the conjunctions of Saturn and Jupiter which are separated by a triple period, that is, about sixty years, will occur rather less than ten degrees apart. They can therefore occur within a single sign (30°) of the zodiac, if the first of the trio is close enough to the beginning of the sign. The character of the sign in which the conjunction occurred was thought to be important, but for the moment we need not go into details. Since the three signs in which successive conjunctions occur are likely to be equally spaced, comprising what is called a triplicity, three suitably chosen conjunctions in a series will be associated with one triplicity - which like the signs themselves was thought to have characteristic properties (fiery, earthy, aery, or watery, and so on). he successive conjunctions, occurring every 20 years, are simply the 'great conjunctions' of the title of Albumasar's book. There was also defined a coniunctio maior, which took place every 240 years, and a coniunctio maxima, which occurred every 960 years. The definitions of these were frequently misunderstood. Bacon, for example, gives a very hazy account in his Opus maius, and leaves us with the impression that he was paraphrasing Albumasar very carelessly. I will explain the periods of 240 and 960 years briefly, and those whose sympathies are with Bacon may omit the next paragraph.
Albumasar opens his Great Conjunctions with a detailed and rather precise account of the mean movements of Jupiter and Saturn, which we can summarize by saying that the conjunctions marked '0' and '3' in the series on the accompanying diagram will be thrice times 2°25'17"10'"6'v apart, or about 7 1/4º.11 We begin as near as possible to the beginning of Aries, in the fiery triplicity. Conjunction number 13, however, will fall into a new triplicity. If we reckon 20 years between great conjunctions, then the 'greater conjunction', when we pass from one triplicity to the next, should happen after 260 years; or, as Albumasar has it, the conjunctions may stay within a triplicity for about 240 years. They will then, by a loose extension of the argument, be in other triplicities for three similar periods, making 960 years in all, after which they will return to the original triplicity. Coniunctio maxima is that conjunction which marks the return to Aries. By virtue of the retrogradations of the planets in practice, and the fact that the figures quoted for the angles are not convenient sub-multiples of 360°, the argument is not precise and not worth discussing in any greater detail.12 What matters is that henceforth those who wished to find patterns in history had three convenient historical periods to conjure with, namely periods of 20, 240, and 960 years.
North, J. D., 1989, Stars, Minds and Fate: Essays in Ancient and Medieval Cosmology. Londres/ Ronceverte: The Hambledon Press.
