[T]his then is the status [and the regular tradition ] of our Evangelical and Apostolic faith, to wit, that as we confess the holy and inseparable Trinity, that is, the Father, the Son and the Holy Ghost, to be of one deity, of one nature and substance or essence, so we will profess also that it has one natural will, power, operation, domination, majesty, potency, and glory. And whatever is said of the same Holy Trinity essentially in singular number we understand to refer to the one nature of the three consubstantial Persons, having been so taught by canonical logic. But when we make a confession concerning one of the same three Persons of that Holy Trinity, of the Son of God, or God the Word, and of the mystery of His adorable dispensation according to the flesh, we assert that all things are double in the one and the same our Lord and Saviour Jesus Christ according to the Evangelical tradition, that is to say, we confess His two natures, to wit the divine and the human, of which and in which He, even after the wonderful and inseparable union, subsists. And we confess that each of his natures has its own natural propriety, and that the divine, has all things that are divine, without any sin. And we recognize that each one (of the two natures) of the one and the same incarnated, that is, humanated (humanati) Word of God is in Him unconfusedly, inseparably and unchangeably, intelligence alone discerning a unity, to avoid the error of confusion. For we equally detest the blasphemy of division and of commixture. For when we confess two natures and two natural wills, and two natural operations in our one Lord Jesus Christ, we do not assert that they are contrary or opposed one to the other (as those who err from the path of truth and accuse the apostolic tradition of doing. Far be this impiety from the hearts of the faithful!), nor as though separated (per se separated) in two persons or subsistences, but we say that as the same our Lord Jesus Christ has two natures so also He has two natural wills and operations, to wit, the divine and the human: the divine will and operation He has in common with the coessential Father from all eternity: the human, He has received from us, taken with our nature in time. This is the apostolic and evangelic tradition, which the spiritual mother of your most felicitous empire, the Apostolic Church of Christ, holds.
This is the pure expression of piety. This is the true and immaculate profession of the Christian religion, not invented by human cunning, but which was taught by the Holy Ghost through the princes of the Apostles. This is the firm and irreprehensible doctrine of the holy Apostles… (Letter to the Sixth Ecumenical Council )