XOR Through the Ages

[sdi]

Please don't think I'm trying to explain geomancy using Mesopotamian mythology or astrology, with which it is clearly not directly connected, but I keep finding cute similarities that I'd like to share. This one comes from Ulla Koch-Westenholz' Mesopotamian Astrology:

A simple rule that is common to all kinds of Babylonian divination is of almost mathematical rigour: within the same omen, a good sign combined with a good sign has a good prediction; good combined with bad means bad; bad combined with bad means good. Expressed algebraically, the rule is also familiar to us: + + = +; + - = -; - - = +. An often quoted example of this rule is found in the astrological texts: if a well-portending planet is bright: favourable (+ + = +); if it is faint: unfavourable (+ - = -); if an ill-portending planet is bright: unfavourable (- + = -); if it is faint: favourable (- - = +).

That is to say, the ancient divinatory practices follow the same binary XOR rule as geomancy does.