Thomas Aquinas

“ Yet it may happen that a person performs an easy deed with as prompt a will as another performs an arduous deed; because he is ready to do even what may be difficult to him. But the actual difficulty, by its penal character, enables the deed to satisfy for sin. ”

“ The first man would not have gained merit in resisting temptation, according to the opinion of those who say that he did not possess grace; even as now there is no merit to those who have not grace. But in this point there is a difference, inasmuch as in the primitive state there was no interior impulse to evil, as in our present state. Hence man was more able then than now to resist temptation even without grace. ”

“ This is in accordance with what the Philosopher says, "Shame, which regards what is ill done, may be found in a virtuous man, but only conditionally; as being so disposed that he would be ashamed if he did wrong" (Ethic. iv, 9) . ”

“ We may also say that, though man was created in grace, yet it was not by virtue of the nature wherein he was created that he could advance by merit, but by virtue of the grace which was added.
Reply to Objection 5: As the motion of the will is not continuous there is nothing against the first man having consented to grace even in the first moment of his existence.
Reply to Objection 6: We merit glory by an act of grace; but we do not merit grace by an act of nature; hence the comparison fails.
Art. 2 - Whether passions existed in the soul of the first man? ”

“ It is accidental to temperance and fortitude to subdue superabundant passion, in so far as they are in a subject which happens to have superabundant passions, and yet those virtues are 'per se' competent to moderate the passions. ”