“‘Greater’ is predicated in bulk, in time, in dignity, in power, or as cause.  The Father cannot be called greater than the Son in bulk, for He is incorporeal:  nor yet in time, for the Son is Creator of times:  nor yet in dignity, for He was not made what He had once not been:  nor yet in power, for ‘what things the Father doeth, these also doeth the son likewise’: John v. 19.  nor as cause, since (the Father) would be similarly greater than He and than we, if He is cause of Him and of us.  The words express rather the honour given by the Son to the Father than any depreciation by the speaker; moreover what is greater is not necessarily of a different essence.  Man is called greater than man, and horse than horse.  If the Father is called greater, it does not immediately follow that He is of another substance.  In a word, the comparison lies between beings of one substance, not between those of different substances. ἐπὶ τῶν ὁμοουσίων οὐκ ἐπὶ τῶν ἑτεροουσίων.