The health-care debate has provided its share of teachable moments. The one at hand has little to do with health care.

The catalyst, the U.S. Conference of Catholic Bishops, supports government-guaranteed health care. However, its support hinges on an amendment barring government funding of abortions.

The bishops' stance infuriated Rep. Patrick Kennedy (D., R.I.). "You mean to tell me the Catholic Church is going to be denying those people lifesaving health care? I thought they were pro-life," he told the Catholic News Service.

Bishop Thomas Tobin of Providence, R.I., pointed out that the bishops do support lifesaving health care for all - including the unborn. Kennedy countered that his support for legal abortion doesn't make him "any less of a Catholic," because the Catholic faith "acknowledges the existence of an imperfect humanity."

Tobin realized that Kennedy was no longer arguing about health policy, but rather about what it means to be Catholic. Unlike some bishops, this protégé of Cardinal Anthony Bevilacqua did not let Kennedy's distortion go unchallenged.

"If you don't accept the teachings of the church, your communion with the church is flawed," he wrote in an open letter to Kennedy last month, "or, in your own words, makes you 'less of a Catholic.' "

Tobin then turned to the real issue: What makes one a Catholic? Baptism? Family? Culture?

More than that, Tobin said. Being a Catholic "means that you believe and accept the teachings of the church, especially on essential matters of faith and morals; that you belong to a local Catholic community, a parish; that you attend Mass on Sundays and receive the sacraments regularly; that you support the church personally, publicly, spiritually, and financially."

Simply put, the church has membership requirements. Kennedy is free to reject them. What he is not free to do is redefine them for himself and condemn the church for not accepting his definition.

But can't what Kennedy calls our "imperfect humanity" lead Catholics to support legal abortion? Tobin made short work of this political philosophizing. Our "imperfect humanity" refers to our common struggles with sins such as anger, pride, greed, impurity, or dishonesty, the bishop said. "Your rejection of the church's teaching on abortion falls into a different category. It's a deliberate and obstinate act of the will; a conscious decision that you've reaffirmed on many occasions."

Kennedy and other politicians have an obligation to review any conflict with the church's core moral teachings with their bishop and determine if it's so grave as to require their leaving either public office or the church. A letter Tobin wrote to Kennedy in 2007 indicated that the bishop felt the matter was grave enough that he should not present himself for Communion.

On MSNBC's Hardball, Tobin was more emphatic: "The point is that any Catholic in public office - his first commitment has to be to his faith ... because it involves your relationship with God," he told Chris Matthews. "And if ... your job gets in the way of your faith, ... you need to quit your job and save your soul. Nothing can become more important than your relationship with God."

In a recent attempt to defend Kennedy, Democratic U.S. Rep. Patrick Murphy of Bucks County said, "We don't legislate at the orders of the Vatican; we legislate what is in our conscience and what we think is good for our country."

I agree. But in 16 years as a Catholic in public office, I never received an order from the Vatican or any clergyman.

I also agree with Murphy - as does the catechism - that Catholics must be true to their consciences. But that is not a free-floating guide that we can define ourselves. A Catholic is required to form his conscience in accordance with the church's teachings on faith and reason, and to act in a morally coherent and consistent way, both privately and publicly.

Finally, the church maintains that there is a natural law that forms the basic moral foundation of society and that can be known through the exercise of reason. Thus, a Catholic public official with a well-formed conscience can arrive at correct moral conclusions not by faith, but by reason.