See J. E. Chisholm, The Pseudo-Augustinian Hypomnesticon against the Pelagians and Celestinans (Vol. I, 1967); J. Pelikan, The Emergence of the Catholic Tradition (1971).
Pelagius taught that the human will, tempered in good deeds and rigorous asceticism, was sufficient to live a sinless life. He told his followers that right action on the part of human beings was all that was necessary for salvation. To him, the grace of God was only an added advantage; helpful, but in no way essential. Pelagius disbelieved in original sin, but said that Adam had condemned humankind through bad example, and that Christ’s good example offered humanity a path to salvation, not through sacrifice, but through instruction of the will. Jerome emerged as one of the chief critics of Pelagianism, because, according to him, Pelagius' view essentially denied the work of the Messiah (Pelagius personally preferring 'teacher' or 'master' to any epithet implying divine power).
Many of the Church Fathers taught that humans have the power of free will and the choice over good and evil. Justin Martyr said that 'every created being is so constituted as to be capable of vice and virtue. For he can do nothing praiseworthy, if he had not the power of turning either way'. 'Unless we suppose man has the power to choose the good and refuse the evil, no one can be accountable for any action whatever.' (Doctrine of the Will by Asa Mahan, p. 61, published by Truth in Heart). Tertullian also argued that no reward can be justly bestowed, no punishment can be justly inflicted, upon him who is good or bad by necessity, and not by his own choice. (ibidem, p. 61). Likewise Origen , Augustine , and Clement of Alexandria
But they also taught that the human race was cursed by the original sin of Adam. Because of the guilt of our first parents, we have been brought into bondage, and made subject to death.
Justin Martyr said, “Let some suppose, from what has been said by us, that we say that whatever occurs happens by a fatal necessity, because it is foretold as known beforehand, this too we explain. We have learned from the prophets, and we hold it to be true, that punishments, chastisements, and good rewards, are rendered according to the merit of each man’s actions. Now, if this is not so, but all things happen by fate, then neither is anything at all in our own power. For if it is predetermined that this man will be good, and this other man will be evil, neither is the first one meritorious nor the latter man to be blamed. And again, unless the human race has the power of avoiding evil and choosing good by free choice, they are not accountable for their actions.”
Justin Martyr said, “I have proved in what has been said that those who were foreknown to be unrighteous, whether men or angels, are not made wicked by God’s fault. Rather, each man is what he will appear to be through his own fault.”
Tatian said, “We were not created to die. Rather, we die by our own fault. Our free will has destroyed us. We who were free have become slaves. We have been sold through sin. Nothing evil has been created by God. We ourselves have manifested wickedness. But we, who have manifested it, are able again to reject it.”
Melito said, “There is, therefore, nothing to hinder you from changing your evil manner to life, because you are a free man.”
Theophilus said, “If, on the other hand, he would turn to the things of death, disobeying God, he would himself be the cause of death to himself. For God made man free, and with power of himself.”
Irenaeus said, “But man, being endowed with reason, and in this respect similar to God, having been made free in his will, and with power over himself, is himself his own cause that sometimes he becomes wheat, and sometimes chaff.”
Irenaeus said, “Let your light so shine before men, that they may see your good deeds’…And ‘Why call me, Lord, Lord, and do not do the things that I say?’…All such passages demonstrate the independent will of man…For it is in man’s power to disobey God and to forfeit what is good.”
Clement of Alexandria said, “We…have believed and are saved by voluntary choice.”
Tertullian said, “I find, then, that man was constituted free by God. He was master of his own will and power…For a law would not be imposed upon one who did not have it in his power to render that obedience which is due to law. Nor again, would the penalty of death be threatened against sin, if a contempt of the law were impossible to man in the liberty of his will…Man is free, with a will either for obedience or resistance.
In contrast, Pelagius taught:
Pelagius said, “Whenever I have to speak on the subject of moral instruction and conduct of a holy life, it is my practice first to demonstrate the power and quality of human nature and to show what it is capable of achieving, and then to go on to encourage the mind of my listener to consider the idea of different kinds of virtues, in case it may be of little or no profit to him to be summoned to pursue ends which he has perhaps assumed hitherto to be beyond his reach; for we can never end upon the path of virtue unless we have hope as our guide and compassion…any good of which human nature is capable has to be revealed, since what is shown to be practicable must be put into practice.”
Pelagius said, "It was because God wished to bestow on the rational creature the gift of doing good of his own free will and the capacity to exercise free choice, by implanting in man the possibility of choosing either alternative...he could do either quite naturally and then bend his will in the other direction too. He could not claim to possess the good of his own volition, unless he was the kind of creature that could also have possessed evil. Our most excellent creator wished us to be able to do either but actually to do only one, that is, good, which he also commanded, giving us the capacity to do evil only so that we might do His will by exercising our own. That being so, this very capacity to do evil is also good - good, I say, because it makes the good part better by making it voluntary and independent, not bound by necessity but free to decide for itself."
Pelagius said, "Those who are unwilling to correct their own way of life appear to want to correct nature itself instead."
Pelagius said, "And lest, on the other hand, it should be thought to be nature's fault that some have been unrighteous, I shall use the evidence of the scripture, which everywhere lay upon sinners the heavy weight of the charge of having used their own will and do not excuse them for having acted only under constraint of nature."
Pelagius said, "Yet we do not defend the good of nature to such an extent that we claim that it cannot do evil, since we undoubtedly declare also that it is capable of good and evil; we merely try to protect it from an unjust charge, so that we may not seem to be forced to do evil through a fault of our nature, when, in fact, we do neither good nor evil without the exercise of our will and always have the freedom to do one of the two, being always able to do either."
Pelagius said, "Nothing impossible has been commanded by the God of justice and majesty...Why do we indulge in pointless evasions, advancing the frailty of our own nature as an objection to the one who commands us? No one knows better the true measure of our strength than he who has given it to us nor does anyone understand better how much we are able to do than he who has given us this very capacity of ours to be able; nor has he who is just wished to command anything impossible or he who is good intended to condemn a man for doing what he could not avoid doing."
Pelagius said, "Grace indeed freely discharges sins, but with the consent and choice of the believer."
Pelagius said, "Obedience results from a decision of the mind, not the substance of the body."
An unknown Pelagian, "Is it possible then possible for a man not to sin? Such a claim is indeed a hard one and a bitter pill for sinners to swallow; it pains the ears of all who desire to live unrighteous. Who will find it easy now to fulfil the demands of righteousness, when there are some who find it hard even to listen to them?"
An unknown Pelagian, "When will a man guilty of any crime or sin accept with a tranquil mind that his wickedness is a product of his own will, not of necessity, and allow what he now strives to attribute to nature to be ascribed to his own free choice? It affords endless comfort to transgressors of the divine law if they are able to believe that their failure to do something is due to inability rather than disinclination, since they understand from their natural wisdom that no one can be judged for failing to do the impossible and that what is justifiable on grounds of impossibility is either a small sin or none at all."
An unknown Pelagian, "Under the plea that it is impossible not to sin, they are given a false sense of security in sinning...Anyone who hears that it is not possible for him to be without sin will not even try to be what he judges to be impossible, and the man who does not try to be without sin must perforce sin all the time, and all the more boldly because he enjoys the false security of believing that it is impossible for him not to sin...But if he were to hear that he is able not to sin, then he would have exerted himself to fulfil what he now knows to be possible when he is striving to fulfil it, to achieve his purpose for the most part, even if not entirely."
An unknown Pelagian, "Consider first whether that which is such that a man cannot be without it ought to be described as sin at all; for everything which cannot be avoided is now put down to nature but it is impious to say that sin is inherent in nature, because in this way the author of nature is being judged at fault… how can it be proper to call sin by that name if, like other natural things, it cannot be avoided, since all sin is to be attributed to the free choice of the will, not to the defects of nature?"