Gregory of Nyssa ( Against Eunomius , 1.15) attacks the notion that the Father has priority in time, and therefore in being, to the Son and Spirit.  Of course, Gregory eventually says that intervals of time have no application to God’s life, but before that he challenges the notion that temporal priority implies superiority in being.  Being doesn’t leak out as time passes.  The dead don’t have any more claim to being than the living.

Gregory puts it this way: “For while the lifetime of the elder as compared with the younger is longer, yet his being has neither increase nor decrease on that account. This will be clear by an illustration. What disadvantage, on the score of being, as compared with Abraham, had David who lived fourteen generations after? Was any change, so far as humanity goes, effected in the latter? Was he less a human being, because he was later in time? Who would be so foolish as to assert this? The definition of their being is the same for both: the lapse of time does not change it. No one would assert that the one was more a man for being first in time, and the other less because he sojourned in life later; as if humanity had been exhausted on the first, or as if time had spent its chief power upon the deceased. For it is not in the power of time to define for each one the measures of nature, but nature abides self-contained, preserving herself through succeeding generations: and time has a course of its own, whether surrounding, or flowing by, this nature, which remains firm and motionless within her own limits. Therefore, not even supposing, as our argument did for a moment, that an advantage were allowed on the score of time, can they properly ascribe to the Father alone the highest supremacy of being.”

Gregory offers this argument as if it were the simplest common sense.  It is not.  All over the ancient world, it was thought that the passage of time diminished the being of man, who slipped from a world of gold into silver into bronze into iron into something even less.  All over the ancient world, time had indeed spent its chief power on the deceased.  In arguing for the Trinity, Gregory is simultaneously proposing a metaphysics of life.