A friend just called and told me to look at this article by R C Sproul.  It gets to the heart of the OP.  
 
What Is Pelagianism?
Now, let’s return briefly to my title, “The Pelagian Captivity of the Church.” What are we talking about? Pelagius was a monk who lived in Britain in the fifth century. He was a contemporary of the greatest theologian of the first millennium of Church history if not of all time, Aurelius Augustine, Bishop of Hippo in North Africa. We have heard of St. Augustine, of his great works in theology, of his City of God, of his Confessions, and so on, which remain Christian classics.
Augustine, in addition to being a titanic theologian and a prodigious intellect, was also a man of deep spirituality and prayer. In one of his famous prayers, Augustine made a seemingly harmless and innocuous statement in the prayer to God in which he says: “O God, command what you wouldst, and grant what thou dost command.” Now, would that give you apoplexy — to hear a prayer like that? Well it certainly set Pelagius, this British monk, into orbit. When he heard that, he protested vociferously, even appealing to Rome to have this ghastly prayer censured from the pen of Augustine. Here’s why. He said, “Are you saying, Augustine, that God has the inherent right to command anything that he so desires from his creatures? Nobody is going to dispute that. God inherently, as the creator of heaven and earth, has the right to impose obligations on his creatures and say, ‘Thou shalt do this, and thou shalt not do that.’ ‘Command whatever thou would’ — it’s a perfectly legitimate prayer.”
It’s the second part of the prayer that Pelagius abhorred when Augustine said, “and grant what thou dost command.” He said, “What are you talking about? If God is just, if God is righteous and God is holy, and God commands of the creature to do something, certainly that creature must have the power within himself, the moral ability within himself, to perform it or God would never require it in the first place.” Now that makes sense, doesn’t it? What Pelagius was saying is that moral responsibility always and everywhere implies moral capability or, simply, moral ability. So why would we have to pray, “God grant me, give me the gift of being able to do what you command me to do”? Pelagius saw in this statement a shadow being cast over the integrity of God himself, who would hold people responsible for doing something they cannot do.
 
This was only part of the article.  To see the rest click this link.
http://www.modernreformation.org/rc01pelagian.htm