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[davidjackson]

The yin/yang concept was very prevalent in medieval texts. Everything was classified male/female, hot/cold, wet/dry, etc.

This is one of the few times I'll disagree with you JPK. You are confusing a binary Taoist concept with a multiple medieval European philosophy.
The Middle Ages (and earlier Roman / Greek) philosopher / medical writers wrote about balance. This was not a duopoly. For example, there were four humours in the body which had to be balanced. The Europeans wrote about balancing the different humours. There was no mention of a duopoly, only of equilibrium between the different forces. How many forces in astrology? Yet the important thing was to find a balance between the forces.
Meanwhile, the Taoist spoke of a duopoly always. Male/Female. Ying / Yang. Good / evil. Two opposing forces, that were always fighting between themselves for control.