This heretical, erroneous way of thinking and acting was countered heavily by the Doctor of Grace, St. Augustine, as well as many others like St. Jerome and ultimately condemned as heretical by several Popes and Councils, most notably the Papal approved Council of Carthage (418).
This Council taught authoritatively what we still profess today, namely: (i) Death did not come to Adam from a physical necessity, but through sin. (ii) New-born children must be baptized on account of original sin. [Note that the current Code of Canon Law emphasizes this must be done within a couple of weeks of birth]. (iii) Sanctifying grace not only avails for the forgiveness of past sins, but also gives assistance for the avoidance of future sins. (iv) The grace of Christ not only discloses the knowledge of God’s commandments, but also imparts strength to will and execute them. (v) Without God’s grace it is not merely more difficult, but absolutely impossible to perform good works. (vi) Not out of humility, but in truth must we confess ourselves to be sinners… (cf. Dz. nos. 101-8).
This is all very interesting in light of what has been transpiring over the last half century or so. In fact, having made this little study, it is amazing to see how much Pelagianism has returned in our own day.