We know what an omphalos actually was, and we have traditions as to what it was believed to be. These traditions seem at first to contradict the monumental evidence, but, as we shall see immediately, both tradition and monumental facts, are equally true and equally essential to any right understanding.
Harrison establishes the methodological charter for omphalos scholarship: monumental and literary evidence must be held together rather than privileging one over the other.
, Themis: A Study of the Social Origins of Greek Religion, 1912thesis