Here is a diagram for a set of four things standing in for each other, as in their being, character, function, or capacity. Qua is a proper English word (from Latin) meaning “as” or “as being” but also “in the function of” or “in the capacity of”. Often used as “A qua A” rather than “A qua B”.
I suppose the diagram could be altered to be four things qua four other things, with apostrophes or something. It could also be altered for a double duality, as shown below, with some nice symmetries.
It is somewhat similar to my diagram of the Tetrameria, but of course arranged differently. The only other example that I can think of as being “Four qua Four” is the Archic Matrix.
Further Reading:
https://www.explainxkcd.com/wiki/index.php/2591:_Qua
https://latin-dictionary.net/definition/32572/quaqua
https://en.wikipedia.org/wiki/Sine_qua_non
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