You posted on the Non Duality forum, which is generally attended by people believing in
Oneness (I'm not one of them), but your mentioning of the
Trinity and
Duality begged my asking:
is Trinity the unifying belief in Duality and Oneness,
as in 3 = 2 + 1 ?
(kidding
)
Interestingly, in Sanskrit their declension has: singular, dual, and plural ...