A common question bedeviling the whole discussion of Baptism is the issue of what the Church means by the “necessity of baptism”. Extremes can be found on both sides.
Some Catholics will insist that all that “necessity of baptism” jazz went out with Vatican II and nobody really believes that stuff anymore. Their rhetoric tends to run along these lines:
“Just so long as you are a good person, it doesn’t really matter if they splashed the water on you. Baptism is an important ritual, of course. One which marks a significant moment in our life as a Catholic family gathering around the Family Table for the Sacred Meal in which we mutually affirm one another as a faith community. But if, for some reason, somebody is not baptized, or has a baptism that is, so-called “invalid” (such as a baptism in the name of the Creator, Redeemer and Sanctifier rather than in those patriarchal terms “Father, Son, and Holy Spirit”), well, don’t worry about it. No big deal.”
At the other polarity are those Catholics who insist that all those not sacramentally baptized are damned. Period.
In between is the Church, which does indeed teach that Baptism is necessary for salvation. That is why we have the uncompromising demand of Jesus, who tells us “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God” (John 3:5). Some Protestant exegetes, desperate to get around the obvious implication of this verse, attempt to claim that the “water” spoken of here is not baptismal water but “amniotic fluid” while “baptism in the spirit” is a totally spiritual phenomenon having nothing to do with water baptism. The problem they face is simply this: nobody anywhere in the Church for century after endless century ever understood the passage to mean anything remotely like this. It was understood by all to refer to plain old ordinary sacramental baptism. If Jesus (and John) mean to tell us “First, you are born by amniotic fluid and then, years later, you are baptized in the Spirit by asking Jesus into your heart as your personal Lord and savior” they could not possibly have chosen a more misleading way of getting their message across. This would have to set some sort of record as an example of the worst pedagogy in the history of the world.
So yes, Jesus teaches that sacramental baptism is necessary—and that the unbaptized Good Thief absolutely, positively made it to heaven (Luke 23:43).
How can this be? Because though we are bound by the sacraments, God is not bound (CCC 1257). In short, it is necessary for us to obey Jesus as far as possible if we hope to be saved, but it is also true that Jesus is not hampered in his power to save if we cannot, through no fault of our own, do as he wills.
Properly understood, the effect of this teaching is threefold. First, it encourages us to not shirk in our obedience to Jesus, since we really are responsible for our choices and we cannot just blow off baptism or change the form and matter of it to suit us. That’s because words really mean things and altering the baptismal formula to something like “Creator, Redeemer and Sanctifier” makes it (in classic Generation Narcissus style) all about us, rather than all about the Blessed Trinity. For Creator, Redeemer, and Sanctifier are titles which describe something of what God does for us, not who he is in himself. Worse still, they are titles which, when used this way, suggest that only the Father creates, only the Son redeems, and only the Spirit sanctifies, when in fact all three Persons are involved in all three actions. It’s a bad idea to begin a life of discipleship by directly ignoring what Christ has explicitly commanded.
The second effect of realizing that we are bound by the sacraments but that God is not bound is this: it teaches us to mind our own business. Our task is to do our best in Christian obedience, not to prognosticate on the fate of people about whom we know nothing. This is a salutary combination since much productive effort can proceed when we stop wasting our time and energy judging others.
Finally, bearing in mind that we are bound by the sacraments while God is not bound frees us to hope. As figures such as the Patriarchs and Prophets, the Holy Innocents, and the Good Thief—as well as unbaptized catechumens—demonstrate, God’s grace is eager to save as many as possible. We must never presume on God’s grace by neglecting to obey him, but we can hope in God’s grace to be far greater than we could ever think or ask (Eph. 3:20-21).