“Many heretics wrongly believe that they exalt grace by contending that it displaces and destroys nature. That amounts to praising God as Giver of grace while insulting and disparaging Him as Creator…we remarked above that they who regard nature as powerless or hold that it is in itself capable of nothing but evil, disparage and affront the Creator’s work. For in the beginning God made all things good, and everything that He makes later is also good, so far as it comes from the Creator’s hand. Therefore I do not have to delay over the blasphemous contention of those heretics who decry the substance of man himself as wholly or partly evil, whether they consider it evil as existing without God, or as coming from the hand of God, or as made evil in consequence of personal or hereditary sin. The last is not entirely foreign to the otherwise subtle Jansenist view, which can without injustice be called the new Manichaeism.
Accordingly the substance and essence of man are good. But if the essence is good, the nature as such must also be good, because it is nothing else than the vital energy springing from the essence and the tendency toward the attainment of the end which the Creator destines for the being in question.
If then, the essence and substance are indestructibly good, the nature as such must also be indestructibly good. Therefore its natural goodness cannot be lost any more than nature itself can, since it is based on the goodness of the essence and proceeds therefrom. Consequently the powers given for the pursuit of natural goods and the inner, necessary striving for such goods cannot be lost. This is so true that even when sin becomes like a second nature in the will, nature continues to resist, and the keenest torment among the devils and the damned themselves consist in this conflict between nature that strives irresistibly for good and the will that is turned against good. And I maintain, furthermore, that such is the case with nature that is burdened with original sin as well as with nature that is not afflicted with original sin. As man’s substance remains the same after sin, nature too is the same.
Because the substance is good, therefore, the vital energy proceeding from it and the tendency toward a destined end must also be good. The proposition that a power striving for development necessarily arises from the essence in every substance, especially in every living and spiritual substance, is, I do not hesitate to say, so firmly established philosophically, that the opposite is thoroughly unphilosophical and incomprehensible. Many philosophers even describe the essence itself as a power that is ever active.
This truth is even more certain in the dogmatic field, for the Church chose this principle as the decisive criterion in its conflict against the Eutychians, Monergetes, and Monotheletes. The Church insistently discerned the resuscitation of Eutychianism in the latter two heresies, because the human nature of Christ, if it really existed, could not be conceived and represented as bereft of power and a tendency toward its own proper activity. And therefore the Church drew from the teaching of those heretics the conclusion that, if Christ’s human nature were completely inactive and motionless, it would cease to be a real nature and a real, existing essence.
Consequently, if every being has a power and inclination for activity, and indeed for good activity, since the power and inclination come from the Creator of the essence and are given by Him, we can say with full right that they who, like the Jansenists, deny every power and inclination toward good in fallen nature, are no less Manichaean than are those Lutherans who often asserted, to the discredit of creation, that man’s substance had become evil. We can say this with the same right as that with which the Church said to the Monergetes and Monotheletes that, by denying all power and energy in the human essence of the Savior, they had relapsed into the Monophysitism of the Eutychians.”
-Matthias Scheeben in Nature and Grace.