Proclus Turns a Pattern Into a Law, and Dionysius Inherits the Law

Plotinus describes procession from the One and the soul's return toward it, but it is Proclus, writing two centuries later and working the scheme into a formal system, who states remaining, procession and return as a triadic pattern applying at every level of reality without exception, not only in the grand movement from the One down to bodies but in the relationship between any cause and any of its effects at any level of the hierarchy. Each effect, on this fuller formulation, remains in its cause even as it proceeds from it, is produced as something genuinely other than the cause, and reverts toward the cause as toward its own good, treated as demonstrable from first principles rather than as a description drawn empirically from how the cosmos happens to behave.

The systematization mattered for what came after Proclus more than for what Plotinus himself had argued. Medieval Christian, Jewish and Islamic thinkers who inherited Neoplatonic emanation generally inherited it in something closer to Proclus's formalized triadic shape than in Plotinus's own less systematic exposition, because it was more directly usable as a structure to be adapted, most consequentially by the writer known as pseudo Dionysius the Areopagite, whose remaining, procession and return language shaped centuries of subsequent Christian mystical theology under an attribution that placed a Neoplatonic system inside an apostolic authority it had never actually held.