Priest

English has one word where the traditions have many, and the flattening it causes is the single most common error in writing about religious office.

A Catholic priest is defined by what ordination authorises him to do at the altar. That is a sacrificial and sacramental definition, and it has a genuine parallel in the Israelite kohen, in the Roman flamen, in the Vedic ritual specialist, all of them men whose function is to perform an act that others may not perform.

It does not describe most of the offices English calls priesthood.

• An imam in ordinary Sunni usage leads prayer, and any competent adult male Muslim may do it. There is no act reserved to him.
• A rabbi is a teacher and a judge. He offers nothing and mediates nothing, and a Jewish service does not require one.
• A granthi attends the Guru Granth Sahib. Sikhism has no priesthood and says so.
• A kannushi manages ritual purity and presents offerings, in a tradition with almost no doctrine for him to hold.
• A bhikkhu has taken a training. He is not a mediator between anyone and anything, and Theravada Buddhism has no god for him to mediate with.

Calling all of these priests puts a Latin Christian shape on offices that were not built to it, and it makes the differences invisible at exactly the point where the differences are the content. This atlas keeps them as separate entries and describes each by its own authorisation.

The requirement that a Latin Catholic priest be unmarried is a discipline of church law, not a teaching about the nature of priesthood, and the church itself is explicit that it could be changed. The evidence is in the church's own practice: Eastern Catholic churches in full communion with Rome ordain married men, and so do the Orthodox churches, whose orders Rome recognises as valid without qualification. If celibacy were doctrinally necessary to priesthood, none of that would be possible.

The rule tightened slowly. Clerical marriage was common in the Western church for its first millennium, and the reforming councils of the eleventh and twelfth centuries, particularly the First and Second Lateran Councils, in 1123 and 1139, moved from discouraging it to declaring the marriages of clerics in major orders invalid. Property was a substantial part of the motive: married clergy had heirs, and heirs inherited church land.

There are married Latin-rite Catholic priests now. Married Anglican and Lutheran clergy who convert have been ordained under provisions dating from 1980 and extended by the personal ordinariates established in 2009. They are a small number and they are a standing demonstration that the rule is a rule.

A discipline can be dispensed. A doctrine cannot. The church treats celibacy as the first and the ordination of women as the second, and the difference between those two answers is the whole of the argument about what is negotiable.