The Catholic, Orthodox and certain other churches use the episcopal governance structure. Bishops in these churches derive their authority from apostolic succession, defined as the uninterrupted transmission of authority from the original apostles through the two millennia of Christianity. Consequently, these churches are extremely concerned about proving apostolic succession, or the idea bishops are direct successors to the Apostles. They believe their current bishops were ordained by other bishops who were ordained by the other bishops in an unbroken chain right back to the time of Jesus.
Apostolic succession is a powerful statement of faith as bishops are ordained by the laying on of hands. In short, current bishops had been touched by the laying on of hands by other bishops who had been touched by other bishops in an unending chain beginning with the Apostles. The Apostles laid their hands on their successors, who laid their hands on their successors in this chain right up to this day. The doctrine of apostolic succession is central to the sacramental validity and also bolsters the use of tradition and not just scripture as the source of authority within the church. This is not a trivial question as the Catholic Church denies the validity of Episcopalian sacraments since it believes their bishops are not validly consecrated.
A great deal of effort is used to document the validity of episcopal consecration. There are websites containing the list of principal consecrator of Catholic bishops back through several hundred years. For instance, the bishop who ordained me as a deacon had an episcopal lineage traceable for approximately 450 years. Understandably, the records become a little murky before then. Apostolic succession can’t be proved for individual bishops before that point, but a strong tradition maintains this continuity.
The Polish National Catholic Church (PNCC) , headquartered in Scranton, Pennsylvania is also concerned about its apostolic succession. A formal schism occurred when Father Francis Hodur led Pennsylvania parishes out of the Roman Catholic Church, setting up the PNCC. The Polish immigrants to the United States had come into conflict with the Roman Catholic hierarchy that was predominantly Irish and German. Issues included the use of Polish in the liturgical setting and ownership of church property. I first became aware of the PNCC when I was a grade-schooler. My home parish had flirted with the idea of becoming a PNCC parish. Later on I studied this church in a doctoral seminar.
At the time of the schism, the Roman Church has recently been roiled by the First Vatican Council. Nationalism was also on the rise, as there was no independent Poland at the time. Poles looked to the Church as the custodian of their culture. A separate Church called the Old Catholic Church had been set up in the Netherlands based on a dispute that originated in the seventeenth and eighteenth centuries. The bishops of the Old Catholic Church were successors of former Roman Catholic bishops who were validly ordained but decided to part ways with their former church. It was the bishops of the Old Catholic Church that ordained Hodur as the first bishop of the PNCC in 1907. Catholic theologians would call this a “valid, but illicit” consecration. Eventually, the PNCC and the Old Catholic Church parted ways as the Old Catholic Church supported the ordination of women to the priesthood. The Old Catholic Church is now in communion with the Anglican Church and a member of the World Council of Churches. Subsequent bishops of the PNCC were ordained by Hodur, maintaining the Apostolic Succession. Even today, members of the PNCC can receive communion in a Roman Catholic Church as the PNCC has maintained apostolic succession and consequently a valid priesthood.