The Six Books of Proclus on the Theology of Plato, Volume 2

For it is necessary that it should either be participated by these, or by other natures, which possess indeed an intellectual essence, but do not always energize intellectually. It is however impossible that it should be participated by the latter of these. For the energy of intellect is immoveable. And hence, the natures by which it is participated, always participate of intellectual energy, which always causes the participants of it to be intellectual. For that which possesses its energy in a certain part of time, is unadapted to be conjoined with an eternal energy. But that which has perfection according to the whole of time, is the medium between every eternal energy, and that which is perfect in a certain time, as well in the mutations of energy, as in essences. For progressions are never effected without a medium, but through kindred and similar natures, both according to hypostases, and the perfections of energies. After a similar manner therefore, every intellect is primarily participated by those beings that are able to perceive intellectually, according to the whole of time, and who always energize intellectually, though their intellection is in time, and is not eternally in energy.