The Enchiridion 108
108 A Mediator Was Necessary to Reconcile Us to God; And Unless This Mediator Had Been God, He Could Not Have Been Our Redeemer PL 40, 282
For we could not be redeemed, even through the one Mediator between God and men, the man Christ Jesus, if He were not also God. Now when Adam was created, he, being a righteous man, had no need of a mediator. But when sin had placed a wide gulf between God and the human race, it was expedient that a Mediator, who alone of the human race was born, lived, and died without sin, should reconcile us to God, and procure even for our bodies a resurrection to eternal life, in order that the pride of man might be exposed and cured through the humility of God; that man might be shown how far he had departed from God, when God became incarnate to bring him back; that an example might be set to disobedient man in the life of obedience of the God-Man; that the fountain of grace might be opened by the Only-begotten taking upon Himself the form of a servant, a form which had no antecedent merit; that an earnest of that resurrection of the body which is promised to the redeemed might be given in the resurrection of the Redeemer; that the devil might be subdued by the same nature which it was his boast to have deceived, and yet man not glorified, lest pride should again spring up; and, in fine, with a view to all the advantages which the thoughtful can perceive and describe, or perceive without being able to describe, as flowing from the transcendent mystery of the person of the Mediator.
Ex Deo salus nostra, ita ut nec per Christum liberaremur, si non esset Deus. Nam neque per ipsum liberaremur unum Mediatorem Dei et hominum hominem Jesum Christum , nisi esset et Deus. Sed cum factus est Adam, homo scilicet rectus, mediatore non opus erat. Cum vero genus humanum peccata longe separaverunt a Deo, per Mediatorem, qui solus sine peccato natus est, vixit, occisus est, reconciliari nos oportebat Deo usque ad carnis resurrectionem in vitam aeternam: ut humana superbia per humilitatem Dei argueretur ac sanaretur, et demonstraretur homini quam longe a Deo recesserat, cum per incarnatum Deum revocaretur, et exemplum obedientiae per hominem Deum contumaci homini praeberetur; et Unigenito suscipiente formam servi, quae nihil ante meruerat, fons gratiae panderetur; et carnis etiam resurrectio redemptis promissa in ipso Redemptore praemonstraretur; et per eamdem naturam quam se decepisse laetabatur, diabolus vinceretur; nec tamen homo gloriaretur, ne iterum superbia nasceretur: et si quid aliud de tanto Mediatoris sacramento a proficientibus videri et dici potest, aut tantum videri, etiamsi dici non potest.