Heretical teaching on grace of Pelagius (355-425), the English or Irish lay monk who first propagated his views in Rome in the time of Pope Anastasius (reigned 399-401). He was scandalized at St. Augustine's teaching on the need for grace to remain chaste, arguing that this imperiled man's use of his own free will. Pelagius wrote and spoke extensively and was several times condemned by Church councils during his lifetime, notably the Councils of Carthage and Mileve in 416, confirmed the following year by Pope Innocent I. Pelagius deceived the next Pope, Zozimus, who at first exonerated the heretic, but soon (418) retracted his decision. Pelagianism is a cluster of doctrinal errors, some of which have plagued the Church ever since. Its principal tenets are: 1. Adam would have died even if he had not sinned; 2. Adam's fall injured only himself and at worst affected his posterity by giving them a bad example; 3. newborn children are in the same condition as Adam before he fell; 4. mankind will not die because of Adam's sin or rise on the Last Day because of Christ's redemption; 5. the law of ancient Israel no less than the Gospel offers equal opportunity to reach heaven. As Pelagianism later developed, it totally denied the supernatural order and the necessity of grace for salvation.
Semi-pelagianism, like Arminianism, allows that God's grace must operate on a man...but is operating on all men (common grace). Then, with this common (prevenient) grace at work, the man is given the choice to follow Christ or reject Christ. This "little island of righteousness", just a tiny atoll, is sufficient to grant the man enough wherewithal to accept or reject the grace needed to save. Although it was also condemned (centuries ago), it has become the theology de jure with Rome today. And now this errant doctrine is not just a problem with Rome...it has permeated much of the so-called Protestant movement.
Augustine stated the definition of a Pelagian and a Semi-Pelagian very well in his Treatise on the Predestination of the Saints. :
But these brethren of ours, about whom and on whose behalf we are now discoursing, say, perhaps, that the Pelagians are refuted by this apostolical testimony in which it is said that we are chosen in Christ and predestinated before the foundation of the world, in order that we should be holy and immaculate in His sight in love. For they think that "having received God's commands we are of ourselves by the choice of our free will made holy and immaculate in His sight in love; and since God foresaw that this would be the case," they say, "He therefore chose and predestinated us in Christ before the foundation of the world." Although the apostle says that it was not because He foreknew that we should be such, but in order that we might be such by the same election of His grace, by which He showed us favour in His beloved Son. When, therefore, He predestinated us, He foreknew His own work by which He makes us holy and immaculate. Whence the Pelagian error is rightly refuted by this testimony. "But we say," say they, "that God did not foreknow anything as ours except that faith by which we begin to believe, and that He chose and predestinated us before the foundation of the world, in order that we might be holy and immaculate by His grace and by His work." But let them also hear in this testimony the words where he says, "We have obtained a lot, being predestinated according to His purpose who worketh all things." [Eph. 1.11.] He, therefore, work-eth the beginning of our belief who worketh all things; because faith itself does not precede that calling of which it is said: "For the gifts and calling of God are without repentance;" [Rom. 11.29.] and of which it is said: "Not of works, but of Him that calleth" [Rom. 9.12.] (although He might have said, "of Him that believeth"); and the election which the Lord signified when He said: "Ye have not chosen me, but I have chosen you." [John 15.16.] For He chose us, not because we believed, but that we might believe, lest we should be said first to have chosen Him, and so His word be false (which be it far from us to think possible), "Ye have not chosen me, but I have chosen you." Neither are we called because we believed, but that we may believe; and by that calling which is without repentance it is effected and carried through that we should believe. But all the many things which we have said concerning this matter need not be repeated.
As Dutchboy rightfully points out, the Church is steeped in Semi-Pelagianism (as well as most of Protestantism).
WE WERE ELECTED AND PREDESTINATED, NOT BECAUSE WE WERE GOING TO BE HOLY, BUT IN ORDER THAT WE MIGHT BE SO.-AUGUSTINE