β) The Jansenists appealed in favor of their teaching to such Patristic passages as the following: “After the withdrawal of the divine assistance he [St. Peter] was unable to stand;”(517) and: “He had undertaken more than he was able to do.”(518) But the two Fathers from whose writings these passages are taken (SS. Chrysostom and Augustine) speak, as the context evinces, of the withdrawal of efficacious and proximately sufficient grace in punishment of Peter’s presumption. Had St. Peter followed our Lord’s advice(519) and prayed instead of relying on his own strength, he would not have fallen. That this was the mind of St. Augustine clearly appears from the following sentence in his work _De Unitate Ecclesiae_: “Who shall doubt that Judas, had he willed, would not have betrayed Christ, and that Peter, had he willed, would not have thrice denied his Master?”(520) c) The theological argument for our thesis may be formulated as follows: Since the state of grace confers a claim to supernatural happiness, it must also confer a claim to those graces which are necessary to attain it. To assert that God denies the just sufficient grace to observe His commandments, to avoid mortal sin, and to persevere in the state of grace, would be to gainsay His solemn promise to His adopted children: “This is the will of my Father that sent me: that every one who seeth the Son and believeth in him, may have life everlasting, and I will raise him up in the last day.”(521) Consequently, God owes it to His own fidelity to bestow sufficient graces upon the just. Again, according to the plain teaching of Revelation, the just are obliged, under pain of sin, to observe the commandments of God and the precepts of His Church.(522) But this is impossible without the aid of grace. Consequently, God grants at least sufficient grace to his servants, for _ad impossibile nemo tenetur_.(523) *Thesis II: In regard to Christians guilty of mortal sin we must hold: (1) that ordinary sinners always receive sufficient grace to avoid mortal sin and do penance; (2) that God never entirely withdraws His grace even from the obdurate.* The first part of this thesis embodies a theological conclusion; the second states the common teaching of Catholic theologians. 1. _Proof of the First Part._ The distinction here drawn between “ordinary” and “obdurate” sinners has its basis in revelation and is clearly demanded by the different degrees of certainty attaching to the two parts of our thesis.