On the Mysteries (De Mysteriis)

...from a genus indeterminate in itself, and a defining difference. For those substances substantia: the underlying reality or "being" of a thing are complete species in every way, existing in a determinate and complete act original: actu; in philosophy, "act" refers to something being fully realized or active, rather than just having the potential to exist. If separable substances substantiae separabiles: spiritual beings like angels or intellects that exist without physical bodies, being simple, do not differ among themselves through specific differences under the same genus, then they do not differ through individual differences under the same species either. Therefore, each one is, as it were, a single genus or a species existing by itself. But they do differ by themselves, by the order of their ranks, and because they relate to the First The "First" refers to the Neoplatonic "One" or God, the source of all existence in different ways.

Intelligences intelligentiae: pure minds that contemplate divine truths without needing logical steps do not agree or differ among themselves by a genus or by any typical differences; for they are most simple. Instead, they differ insofar as they relate to the First either in the same or in a different manner; some are arranged in higher and others in subsequent ranks of perfection. The differences of things among themselves in their actions and their passions original: passionibus; here meaning "passivity" or how a thing is acted upon by others must always be resolved into differences of their powers, and these into differences of their essences essentia: the "what-it-is" of a thing; its core nature. One must not stop at the effects, but proceed to the prior causes.

Neither in the higher substances nor in our own soul is there any passive motion; rather, everything is an effective act. The motion of the soul, by which it moves from itself, is not divided into a "mover" and a "moved," or into "moving" and "being moved," but is an essential act proceeding...