Many Churches, including the Roman Catholic Church, claim to be "Apostolic". What they mean be this is that they derive their claims to authority from From Jesus himself through at least one of the twelve Apostles. This authority is handed on from generation to generation, generally from bishop to bishop. According to the theory, the twelve apostles passed on their authority to bishops, their successors. These successor bishops handed on their authority to their successors, and so on. (This is why at least one existing bishop is needed to consecrate a new bishop. In practice several bishops often take part to ensure that their can be no possibility of questioning a valid chain). In theory any modern bishop claiming apostolic succession could trace his authority back to at least one apostle, through a chain of predecessors.
Medieval Catholic theologians noted that the Cathars claimed a similar succession for the Parfaits. Only Parfaits could create new Parfaits (through the Consolamentum), and since the first Parfaits were the apostles, initiated by Jesus into the secret inner knowledge, any Cathar Parfait had a claim to authority that paralleled that of Catholic bishops. Catholics always had an explanation for non-Catholic practices that were similar to their own. They were obviously perversions of the true Catholic doctrine. The Cathars had simply copied and perverted the theory of apostolic succession.
The evidence shows almost exactly the opposite. The theory of apostolic succession was first recorded by a gnostic sect in the third century. The idea seemed such a good one that it was picked up by other strands of Christianity - including the one that gave rise to the Roman Catholic Church. The unfortunate lacunae between the apostles and the contemorary third cenury bishops could easily be filled by the invention of suitable chains of predessor bishops, and so it was. (Genuine contemporary continuous lists of bishops from this period are unknown, except for a line of bishops of Jerusalem who, unfortunately for the Roman Catholic case, were practicing Jews).
Although it is something of a simplification, one might reasonably claim that the Roman Catholic Church stole the idea of apostolic succession from the Cathars, rather than the converse.



