Quintessence

Quintessence was a term for a "hidden variable" which could be used to reconcile two contradictory but valuable beliefs.

The term originated in alchemy, where it was the "spirit" which infused and informed the four classical elements. A late 20th century form of quintessence was dark matter, an assumption which reconciled the movement of galaxies with scientists' gravitational calculations. (PROSE: The Book of the War)

In archemathics, the quintessence was a layer of reality described as "the most fundamental level of being". All matter and meaning in the Spiral Politic was inscribed on the quintessence. (PROSE: Against Nature)

In reference to quintessence's intermediary role, the House Military included a rank called Quintessence, mediating the gap between House strategists and other, more traditional military roles. (PROSE: The Book of the War)