403 Following St. Paul, the Church has always taught that the overwhelming misery which oppresses men and their inclination towards evil and death cannot be understood apart from their connection with Adam’s sin and the fact that he has transmitted to us a sin with which we are all born afflicted, a sin which is the “death of the soul”. 291 Because of this certainty of faith, the Church baptizes for the remission of sins even tiny infants who have not committed personal sin. 292
405 Although it is proper to each individual, 295 original sin does not have the character of a personal fault in any of Adam’s descendants. It is a deprivation of original holiness and justice, but human nature has not been totally corrupted: it is wounded in the natural powers proper to it, subject to ignorance, suffering and the dominion of death, and inclined to sin - an inclination to evil that is called concupiscence". Baptism, by imparting the life of Christ’s grace, erases original sin and turns a man back towards God, but the consequences for nature, weakened and inclined to evil, persist in man and summon him to spiritual battle.
161 Believing in Jesus Christ and in the One who sent him for our salvation is necessary for obtaining that salvation. 42 “Since “without faith it is impossible to please [God]” and to attain to the fellowship of his sons, therefore without faith no one has ever attained justification, nor will anyone obtain eternal life ‘But he who endures to the end.’” 43
291 Cf. Council of Trent: DS 1512.
292 Cf. Council of Trent: DS 1514.
295 Cf. Council of Trent: DS 1513.
42 Mk. 16:16; Jn 3:36; 6:40 et al.
43 Dei Filius 3

S 3012; cf. Mt 10:22; 24:13 and Heb 11:6; Council of Trent

S 1532.