Protestant counter-claims to the Catholic interpretation are largely based on the difference between the Greek words translated "Rock" in the Matthean passage. In classical Attic Greek "petros" generally meant "pebble," while "petra" meant "boulder" or "cliff". Accordingly, taking Peter's name to mean "pebble", they argue that the "rock" in question cannot have been Peter, but something else, either Jesus himself, or the faith in Jesus that Peter had just professed. However, the New Testament was written in Koiné Greek, not Attic Greek, and some authorities say no significant difference existed between the meanings of "petros" and "petra".