Intrigued by the mysteries of the "Sleeping Prophet", Edgar Cayce, Lehner "found that [my] initial notions about the ancient civilization along the Nile could not stand up to the bedrock reality of the Giza Plateau".[2] He turned to the scientific method of discovery in order to understand the culture better, returning some years later to complete a doctoral degree at Yale University. Lehner's 1991 dissertation was titled Archaeology of an image: The Great Sphinx of Giza.