Guthrie-Plotinus: agency

Those sages who (like Leucippus, Democritus   and Epicurus  ) assumed material principles such as the atoms, and who explain everything by their motion, their shock and combinations, pretend that everything existent and occurring is caused by the agency of these atoms, their “actions and reactions.” This includes, according to them, our appetites and dispositions. The necessity residing in the nature of these principles, and in their effects, is therefore, by these sages, extended to everything that exists. As to the (Ionic Hylicists), who assume other physical (ultimate) principles, referring everything to them, they thus also subject all beings to necessity. [Ennead III,1 (3) 2]

To begin with, this Necessity and Fate would by their excess destroy themselves, and render impossible the sequence and concatenation of the causes. It is, indeed, absurd to insist that our members are moved by Fate when they are set in motion, or innervated, by the “governing principle.” It is a mistake to suppose that there is a part which imparts motion, and on the other hand, a part which receives it from the former; it is the governing principle that moves the leg, as it would any other part. Likewise, if in the universe exists but a single principle which “acts and reacts,” if things derive from each other by a series of causes each of which refers to the preceding one, it will no longer be possible to say truly that all things arise through causes, for their totality will constitute but a single being. In that case, we are no longer ourselves; actions are no longer ours; it is no longer we who reason; it is a foreign principle which reasons, wills, and acts in us, just as it is not our feet that walk, but we who walk by the agency of our feet. On the contrary, common sense admits that every person lives, thinks, and acts by his own individual, proper life, thought and action; to each must be left the responsibility of his actions, good or evil, and not attribute shameful deeds to the universal cause. [Ennead III,1 (3) 4]