It has become commonplace nowadays to insist that obligatory celibacy is not the cause of the sexual-abuse crisis in the priesthood. The recent report of the independent, but episcopally-appointed, National Review Board makes that point.

One wonders if perhaps its lay membership felt the need to give something back to a hierarchical establishment that would likely be uncomfortable with most of its findings.

It may be that there are some uninformed, simplistically-minded people out there who have claimed that celibacy is the cause of this terrible scandal and crisis, but I am not aware of a single serious commentator who has made such a claim.

The defenders of celibacy are surely right when they ask, "If celibacy were the cause of the crisis, why haven't the overwhelming majority of celibate priests been sexually involved with children and young people?"

But those same defenders move onto softer ground when they cite the statistic that "only" four percent of celibate priests have been guilty of these crimes and sins of sexual abuse. From there they move almost effortlessly to the conclusion that 96 percent of celibate priests are faithful to their commitment to celibacy.

But this is a fallacy. Sexual involvement with children and young people is not the only way that celibacy can be violated. The fact that at least four percent of priests have abused children and teenagers does not necessarily mean that the remaining 96 percent are celibate in the full sense of the word.

Such an assumption is at least questioned, if not contradicted, by the testimony and experience of spiritual directors, psychologists, vicars for clergy, and, most importantly, of priests themselves. They know that celibacy does not work in the way that church officials and many, if not most, laity assume it works.

Richard Sipe's recently published book, Celibacy in Crisis: A Secret World Revisited (New York: Brunner-Routledge, 2003), challenges the celibacy-is-working-for-the-other-96-percent thesis. On the basis of hundreds of interviews with priests, their partners, and their victims, Sipe concludes that at any one time one-half of the priest population involve themselves with sexual activity of some sort.

He further estimates that at any one time only two percent of celibate clergy can be said to have truly "achieved" celibacy, that is, of having successfully negotiated each developmental stage in their lives as persons and as priests so that their celibate state can be described as "irreversible."

Another six to eight percent for whom the practice of celibacy is "firmly established" have apparently been gifted with the "clear charism of celibacy," occasional lapses over the course of a lifetime notwithstanding.

If Richard Sipe's findings are valid, it requires no mathematical dexterity to see that for a significant number of priests, celibacy either does not work at all or is vulnerable to frequent or occasional compromises of one sort or another.

Again, this is still not to say that obligatory celibacy is the cause of the crisis. Rather, it is a major factor, but not in isolation from the church's official teachings on all aspects of human sexuality nor from the way in which those teachings have been communicated to, and internalized by, clergy, religious and laity alike.

By restricting ordination and the continued exercise of priestly ministry to those willing to commit themselves to life-long celibacy, the Roman Catholic Church is forced to draw from an exceedingly narrow slice of its male population for its most important pastoral ministry, a ministry that is indispensable to the church's sacramental life, without which the church cannot function as church.

Within that narrow slice of the Catholic population, there is likely to be a disproportionately higher percentage of sexually dysfunctional or immature individuals than in the general male population, and there is also likely to be a disproportionately higher number of homosexuals, many of whom may have a true vocation to the priesthood, but others of whom may have been attracted, sub-consciously or not, to the "cover" that a celibate priesthood offers.

The sexual-abuse scandal has undoubtedly changed public perceptions in this regard.

Defenders of the status quo sometimes point to surveys that show that the majority of priests would not marry, even if given the choice. What they do not add, however, is that the majority of those same priests nonetheless believe that celibacy should be optional.

One final question: If celibacy has nothing to do with the sexual-abuse crisis, why is it that the scandal has not touched in any significant way the non-Roman, Eastern-rite Catholic churches, which have a married priesthood?

Father Richard P. McBrien is the Crowley-O'Brien Professor of Theology at the University of Notre Dame.