By convention sweet and by convention bitter,
By convention hot, by convention cold,
By convention color; but in reality atoms and void.
The ancient and archaic system of medicine called Humorism still has associations with modern psychological investigations via analogies with the Four Temperaments. Mentioned more for completeness, the four qualities of Humorism (Hotness, Coldness, Dryness, Wetness) may be considered linked to other fourfolds presented here such as the Four Seasons, the Four Elements, and as I mentioned the Four Temperaments.
These are called the four qualities because four relations between the Four Elements generate them, out of the six possible. Dryness is the relationship between Fire and Earth, Hotness is between Air and Fire, Wetness is between Water and Air, and Coldness is between Earth and Water. Alternatively, one can say Air has the qualities of being Hot and Wet, Fire is Hot and Dry, Water is Cold and Wet, and Earth is Cold and Dry.
As such these relations can be considered lying between the poles of the Four Elements. Along with the elements they may form a double square star, or two squares within a regular octagon. I’m not sure if this figure has a special name: in the anime “Inuyasha: the Final Act”, “Kagome” was this double square figure as well as the name of a major character. However “Kagome” actually seems to mean a different symbol: a star formed by two triangles within a regular hexagon. We don’t talk much about triads here.
There is also a children’s game called “Kagome Kagome”, where one child is centered within a ring of others, circling and chanting a song. The central child is only released if she can guess who is behind her when the chant stops. No peeking! Perhaps this position is reserved for reality or metaphysics in our representations.
These two axes can also be thought to encircle typical earth-type organisms within their habitable zones of humidity and temperature: neither too cold nor too hot, neither too dry nor too wet. This is known as a “Goldilocks effect”, after “Goldilocks and the Three Bears”. Also, the desirable middle between extremes is often called the “Golden Mean”, or the “Happy Medium”.
If humidity is considered to be a Cosine wave, and temperature is considered a Sine wave, then the Four Seasons can be located where x = 0 (Spring), π/2 (Summer), π (Fall), and 3π/2 (Winter). Q.E.D.!
[*8.36, *8.107, *9.6]