Hilary of Poitiers

(viii. de Trin. c. 5) The heretics, since they cannot gainsay these words, endeavour by an impious lie to explain them away. They maintain that this unity is unanimity only; a unity of will, not of nature; i. e. that the two are one, not in that they are the same, but in that they will the same. But they are one, not by any economy merely, but by the nativity of the Son’s nature, since there is no falling off of the Father’s divinity in begetting Him. They are one whilst the sheep that are not plucked out of the Son’s hand, are not plucked out of the Father’s hand: whilst in Him working, the Father worketh; whilst He is in the Father, and the Father in Him. This unity, not creation but nativity, not will but power, not unanimity but nature accomplisheth. But we deny not therefore the unanimity of the Father and Son; for the heretics, because we refuse to admit concord in the place of unity, accuse us of making a disagreement between the Father and Son. We deny not unanimity, but we place it on the ground of unity. The Father and Son are one in respect of nature, honour, and virtue: and the same nature cannot will different things.