
1) Christian philosophy
Found on
https://www.crosswordclues.com/clue/trialism

Trialism in philosophy was introduced by John Cottingham as an alternative interpretation of the mind-body dualism of Rene Descartes. Trialism keeps the two substances of mind and body, but introduces a third attribute, sensation, belonging to the union of mind and body. This allows animals, which do not have thought, to be regarded as having sens...
Found on
http://en.wikipedia.org/wiki/Trialism

doctrine that humans have three separate essences (body, soul, spirit)
Found on
http://phrontistery.info/t.html
No exact match found.