Al Biruni & Ptolemy on Aspects


Abu Ma’shar

This is one more very brief introduction to the schemata of astrological aspects as expressed by Al Biruni in his Book of Instruction. The aspects he uses include the Inconjunct or Quincunx, refered to by Claudius Ptolemy as an aversion, rather than an aspect . Al Biruni has discussed the Inconjunct immediately before the insertion of the schemata. Oddly enough he opts not to include it in the visual presentation but gives a full written explanation. We will lok at what he has to say as well as Ptolemy’s comments on the subject in his Tetrabiblos.

Al Biruni provides a commentary for the schemata. Much of it is self explanatory, such as Gemini and Sagittarius forming and opposition. In section 373 he writes:

As the complex must follow the simple,we have now to consider the relations of the signs to each other.

Each sign is in Sextile aspect to the third and seventh left and right of it, and there is s sixth of the zodiac (60 ° ) between any degre of that sign and the same degree of those named. Similarly the Quartile aspect is a between a sign the fourth and tenth, left and right,  separated by 90  ° , and the Trine between the fifth and ninth, distant 120°  and the Opposite sign is the the seventh, 180 ° There are therefore seven signs to which the sign in question turns its face and which are consequently considered to be bound in aspect to it. The two signs which are each side of the one in question and their opposites viz. the second and the twelfth and the sixth and the eighth are not in aspect and are inconjunct. (Instructions p. 20).


In section 375 though he discusses the relative strength or “power” of the aspects:

The  following is the order of power of the various aspects. The most powerful is Conjunction. i.e. meeting in the same same, then the opposite [Opposition] then the dexter Quartile, sinister Quartile, dexter Trine, sinister Trine, dexter Sextile, sinister Sextile, When there are two aspects the powerful renders the weaker one incompetent and takes away its power.  (Instruction 21).

Ptolemy writes :

All signs, between which there does not exist any familiarity in any of the modes above specified, are inconjunct and separated. For instance, all signs are inconjunct which are neither commanding nor obeying, and not beholding each other nor of equal power, as well as all signs which contain between them the space of one sign only, or the space of five signs, and which do not at all share in any of the four prescribed configurations: viz. the opposition, the trine, the quartile, and the sextile.Aspects-ptolemy-tetrabiblos-1533_Hervagius

All parts which are distant from each other in the space of one sign only are considered inconjunct, because they are averted, as it were, from each other; and because, although the said space between them may extend into two signs, the whole only contains an angle equal to that of one sign: all parts distant from each other in the space of five signs are also considered inconjunct, because they divide the whole circle into unequal parts; whereas the spaces contained in the configurations above-mentioned, viz. the opposition, trine, quartile, and sextile, produce aliquot divisions.

(Tetrabiblos p. 27)

Although there is overall agreement, there are significant differences. Ptolemy doesn’t specifically mention the Conjunction that Al Biruni put at the top of the list of aspect power is concerned. I get the impression that here is simply taking it for granted.  He was universally understood as including the Conjunction as far as I know.Astronomes_-_miniature_ottomane_XVIIe

Ptolemy makes no distinction between Dexter and Sinister. Most importantly, he doesn’t provide a hierarchy of power to the aspects at all. Neither Al Biruni nor Ptolemy discuss aspect patters, such as Grand Trines, Grand Crosses or even T- Squares.

Al Biruni’s statement that the most powerful aspect renders the weaker one incompetent is broad in its compass. When reading a specific chart we may have some difficult choices to make in judgement but he dose provide us many toosl to make that choice easier. However, as the statement stands alone, it seems reductionist.

Consider for a moment a hypothetical chart with a tight Air Trine. One of the   planets is forming a square or opposition to a fourth planet. Particularly if the square is applying, that is very strong aspect. It may even be  in aspect to a malefic, making it far worse. But I still can’t see how the grand trine is entirely erased from the equation.. massively weakened perhaps but not without any life at all.

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