I've always assumed that "mens" = rationality , and that "animus" =
Aristotle's rational soul of humans; leaving "anima" to be something
like "soul" (Greek ψυχή). But after a search through Cicero and Vergil,
all I can say is that they confused them utterly.
in primis regina quietum
accipit in Teucros animum mentemque benignam
(Aeneid I)
Principio caelum ac terras camposque liquentis
lucentemque globum lunae Titaniaque astra
spiritus intus alit, totamque infusa per artus
mens agitat molem et magno se corpore miscet
(Aeneid VI)
"Mens agitat molem"; mind moves matter, spread through the limbs.
That's not much different from the souls in Homer; they're like ghostly,
shimmering, translucent images of the body, and they come out of dead
ones and go flitting and whittering down to Hades.
Ed