A philosophically-minded young friend recently sent me a fine rant, after having watched a presidential candidates' cattle call on CNN. The discussion had focused on religion.

Several candidates, who identified themselves as Catholics, had indicated that their Christianity was rather easily bracketed when they put on their hats as public servants. "Does ontology mean nothing to these people?" my friend asked. "Do they even know what it is?"

Well, no. They don't. And that's a problem.

By "ontology," my correspondent was using the technical vocabulary of philosophy to re-capture an image once familiar to generations of Catholics from the Baltimore Catechism, the image of an "indelible mark" imprinted on the soul by certain sacraments. This image of the "indelible mark" was intended to convey a basic truth of Catholic faith: that the reception of certain sacraments changed the recipient forever, by conferring on him or her a new identity --- not in the psychological sense of that overused term, but substantively. Or, if you'll pardon the term, ontologically.

Baptism is a sacrament with what we might call ontological heft. To become a Christian through baptism is qualitatively different from becoming a citizen, a member of the Supreme Court bar, a Detroit Tigers fan, a collector of vintage Volvos, a bourbon drinker, a member of the Democratic or Republican parties, a lifelong student of Dante, or a trout fisherman.

When one becomes a Christian through baptism and the outpouring of the Holy Spirit, one is changed in a fundamental way. As St. Paul taught those rowdy Corinthians, one becomes a "new creation" (2 Cor 5: 17).

That ontological change in baptism (and I swear that's the last time I'll use the o-word) incorporates a Catholic into the Church. The Church is not incidental to our identity as new creations in Christ; we don't "join" the Church the way we join the Rotary, the Kiwanis, the American Association of University Women, the A.M.A., the American Legion or my beloved Society for the Restoration of Lost Positives ("ept," "ert," etc.).

Being a Catholic Christian engages who-I-am in a substantively different way than any other aspect of my "identity" --- not because I think that's the case, or because I feel that's the case, but because that is the case: objectively, not subjectively. Baptism has real effects; it changes us forever.

So when a candidate for public office avers, on the one hand, that his or her "membership in the faith community" is deeply personal, or a matter of "my relationship with Jesus," and then suggests that being a Catholic Christian is a compartment of life that can be hermetically sealed off from first principles of justice (i.e., the principles involved in abortion, euthanasia and embryo-destructive stem-cell research), we're dealing with a confused camper --- one might even say, a camper with a severe identity-crisis.

That most Catholic politicians don't understand this is obvious: that's why, were the entire Catholic contingent in Congress to be replaced by Mormons, Capitol Hill would certainly lose some good people --- but the social doctrine of the Church and the Church's teaching on the life issues (both of which involve publicly accessible moral truths, not sectarian "positions") would have a better chance of implementation.

The politicos aren't alone, however. How many Catholics in the United States understand that their baptism made them a "new creation"? Decades of faux-catechesis, in which the only "indelible marks" to be found in religious education classrooms were made by magic markers on felt banners, have left us severely weakened in our self-understanding, such that too many Catholics imagine their Christianity to be the religious variant of their membership in other voluntary organizations. Thus the challenge posed to the official teachers of the Church --- especially bishops and pastors --- is a massive one.

Given the campaign calendar, we'll soon be embroiled in another round of the religion-and-politics wars. Reminding all Catholics about what baptism really does to us would be a good place to begin calling the office-seekers to account.

George Weigel is a senior fellow of the Ethics and Public Policy Center in Washington, D.C.