Since we know that integrity was really possessed by Adam, and that is was lost in the Fall, it is certain that we are inclined to sin, without the help of grace.
For what
Pelagianism and
Semi-Pelagianism are. Fr. Hardon, S.J., explained:
Pelagianism. …
Its basic principle is the affirmation of the self-sufficiency of man’s free will. We can always will and do good, even when de facto we will and do otherwise, depending entirely on our own moral strength.
In the Pelagian scheme there is no room for original sin. What we now call preternatural gifts of bodily immortality and integrity were never really possessed by Adam. He left us only a bad example. The fact that we are prone to sin is not inherited from Adam and Eve, our first parents. We acquire it by our own misdeeds.
Baptism therefore can have no strict remissive function. A person can be saved without it. At most its purpose is to incorporate us into the Church, unite us with Christ, or make us members of a mysterious heavenly kingdom. It can never be understood as being absolutely necessary for salvation.
For the same reason, sanctifying grace is not the necessary basis of supernatural activity, but only a sort of remedy for actual sins or a spiritual adornment of Christians and a sign of their divine adoption. …
Semi-Pelagianism. “Half-Pelagianism” or Semi-Pelagianism was historically linked to its predecessor. In this theory grace is admittedly necessary, but not ordinarily for the first steps towards the Christian life, and also not for final perseverance in the grace of God.
therealpresence.org/archives/Grace/Grace_009.htm
Ca
techism
406 The Church’s teaching on the transmission of original sin was articulated more precisely in the fifth century, especially under the impulse of St. Augustine’s reflections against Pelagianism, and in the sixteenth century, in opposition to the Protestant Reformation. Pelagius held that man could, by the natural power of free will and without the necessary help of God’s grace, lead a morally good life; he thus reduced the influence of Adam’s fault to bad example. The first Protestant reformers, on the contrary, taught that original sin has radically perverted man and destroyed his freedom; they identified the sin inherited by each man with the tendency to evil (concupiscentia), which would be insurmountable. The Church pronounced on the meaning of the data of Revelation on original sin especially at the second Council of Orange (529)296 and at the Council of Trent (1546).297