Catholic theology holds that bishops stand in unbroken succession from the apostles, apostolic succession, understood as guaranteeing the continuity of the Church's teaching authority and sacramental validity across two thousand years; tracing an individual bishop's own consecration lineage back through named predecessors is a genre of ecclesiastical record-keeping with genuine historical depth, though gaps and uncertainties exist for some medieval lines. A candidate is ordained a bishop by at least one, and normatively three, already-consecrated bishops, a plurality intended partly to demonstrate collegial consent to the new bishop's entry into the episcopal college and partly, historically, as a safeguard of validity in an era before centralized documentation could otherwise confirm it.
Episcopal appointment today follows a process centered on the Congregation for Bishops in Rome, which reviews candidates proposed through consultation involving the local papal nuncio, existing bishops of the province and, less formally, other clergy and laity, before the Pope makes the final appointment; the practice contrasts with earlier centuries in which secular rulers, cathedral chapters or local nobility often held decisive influence over episcopal selection, a tension, the investiture controversy of the eleventh and twelfth centuries being its sharpest medieval expression, that shaped much of the relationship between the papacy and European states.