Catholic priests weren't always required to be celibate, and women may have held priestly roles?

• Married priests were common through Catholicism's first 1,000 years. But most scholars agree that priests have been required to abstain from sex and to remain unmarried since the First Lateran Council declared clerical marriages invalid in 1123. There's debate about why the change was made, but some speculate the Vatican feared priests' assets would be inherited by their children, instead of the church. Others say celibacy was a means to separate priests from a sinful world.

The celibacy rule is not considered doctrine; that is, it is not rooted in the Bible. Therefore, it could be changed by a decree from the Vatican. But the Pope does not favor such a change, saying a priest can best serve his flock if he is solely devoted to his church, rather than to a wife and family.

• Unlike the celibacy rule, the ban on women priests is considered by many to be based on Biblical teachings, and therefore is not subject to change. Catholics who favor women in the priesthood, however, note that archaeologists have found ancient frescos that appear to show women presiding over Masses. They also say the Bible's frequent references to women, such as Mary Magdalene, suggest they had leadership roles.

Conservative Catholics say priests represent Christ on Earth and, like the Apostles before them, should always be men.