William R. Callahan | Dissident priest, 78

William R. Callahan, 78, a Roman Catholic priest and self-described "impossible dreamer" whose determined opposition to Vatican policies prompted Jesuit officials to expel him from their order, died Monday in Washington.

The cause was complications of Parkinson's disease, said the Quixote Center, an organization that Dr. Callahan helped found to press for changes in the church and society. It is independent of the church and based in Brentwood, Md. He lived there.

Born in Scituate, Mass., Dr. Callahan earned a doctorate in physics from Johns Hopkins University in 1962. While pursuing the degree, he worked for NASA on weather satellites. He then moved to Connecticut to teach physics at Fairfield University, a Jesuit institution. He was ordained as a priest in 1965.

Like Cervantes' fictional character who inspired the center's name, Dr. Callahan tilted at windmills and never accomplished his major goals, the biggest of which was ordaining women as priests. But he was a thorn in the church's side for a generation.

"Bill tried to be a prophetic voice in the church, a voice crying in the wilderness," said Thomas J. Reese, a senior fellow at the Woodstock Theological Center at Georgetown University.

Dr. Callahan remained a priest after his expulsion from the Jesuit order, the Society of Jesus, in 1991, but the church barred him from acting as one.

He aggravated church officials during the U.S. tour of Pope John Paul II in 1979 by imploring priests to refuse to help the pope in celebrating Mass. Dr. Callahan's hope was that more lay women would then have to be enlisted to assist at the services.

He told the Washington Post in 1989 that he was simply "following the example of Jesus, who was never willing to shut up."

He started the Quixote Center in 1976 with Dolly Pomerleau, who became a work partner of his for many years. They married days before he died. - N.Y. Times News Service