就信仰生活的因果秩序而言，聖洗聖事對任何其他的聖事而言都須是在先。按天主教的信仰，聖洗聖事使人與基督結成一體，成為天主的子民，獲得一切罪過的赦免。因為誰受洗，就是藉著同基督相似的死亡，而與祂結合，也與祂同死同葬，並且在祂內與祂同生一起復活。人藉聖洗從罪惡的死亡中被解放出來，進入生命。因此聖洗可謂是跨越死亡的新生，透過與基督之死結合，使人跨入一種有別於以往的全新基督徒生命。為說明聖洗聖事如何改變人本性，本文分六個部分循序說明。首先，指出人類由始祖所繼承的本性在接受聖洗前的本性；再者，說明聖洗的意義；三，說明聖洗的效果；四，解釋聖洗除罪的原因與聖洗的本質；五，說明基督徒在聖洗之後既然得到聖神的助佑為何還會犯錯 ？最後，以神學人類學的觀點，說明何謂基督徒的生命。

Regarding the cause-and-effect order of religious life, baptism is prior to other sacraments. According to the Catholic faith, baptism unites one with Jesus Christ, makes him one of God’s children and absolves all his sins. Because whoever that is baptized is combined, deceased and buried with Jesus through a death similar to His; and then the one who is baptized would revive within and along with Him. Through baptism, one is released out of the sinful death and into life. Therefore, baptism is a rebirth beyond death; united with the death of Jesus, baptism brings one into an unprecedented new life of a Christian. Here, it is explained in six parts how baptism changes human nature. First, it is pointed out the nature one inherits from the ancestors is the pre-baptism nature. Second, the meaning of baptism is explained. Third, the effect of baptism is explained. Fourth, the absolution and nature of baptism is accounted for. Fifth, we explain why Christians still err after they are baptized and obtain the blessing of the Holy Ghost. And, finally, the life of a Christian is explained from the perspective of theological anthropology.