9 But another passage is also seized by those who are fighting against God to the perversion of their hearers: I mean the words “The Son can do nothing of Himself.” To me this saying too seems distinctly declaratory of the Son's being of the same nature as the Father. For if every rational creature is able to do anything of himself, and the inclination which each has to the worse and to the better is in his own power, but the Son can do nothing of Himself, then the Son is not a creature. And if He is not a creature, then He is of one essence and substance with the Father. Again; no creature can do what he likes. But the Son does what He wills in heaven and in earth. Therefore the Son is not a creature. Again; all creatures are either constituted of contraries or receptive of contraries. But the Son is very righteousness, and immaterial. Therefore the Son is not a creature, and if He is not a creature, He is of one essence and substance with the Father.
Source: Letters (New Advent)