These explanations of the fundamental questions of ecclesiastical art grew essentially out of a two-hour lecture. As lecturer on sacred art and chairman of the St. Poelten committee on art, I was permitted to give this lecture to the philosophical-theological Diocesan Academy at St. Poelte at the invitation of His Eminence, the Most reverend Cardinal Archbishop Dr. Theodor Innitzen, with the approval of the administration of the Catholic Academy of Vienna. It was delivered on April 23, 1953, at Schotten Abbey in appreciation of the instruction on Christian art given by the Holy Office on June 30, 1952.