“Even when Jesus’ sayings are found in two or three gospels, they don’t consider this as passing the ‘multiple attestation’ criterion. If a saying is found in Matthew, Mark, and Luke, they consider that only one source, because they assume that Matthew and Luke used Mark in writing their gospels. They’re failing to recognize that an increasing number of scholars are expressing serious reservations about the theory that Matthew and Luke used Mark. With this line of thinking, you can see why it’s extremely difficult to prove multiple attestation.”
