Where there is no spiritual life, something external must exist as an assurance of ecclesiality. A specific function, the pope, or a system of functions, a hierarchy-that is the criterion of ecclesiality for Roman Catholics. On the other hand, a specific confessional formula, the creed, or a system of formulas, the text of the Scripture, is the criterion of ecclesiality for Protestants. In the final analysis, in both cases what is decisive is a concept, an ecclesiastical-juridical concept for Catholics and an ecclesiastical-scientific concept for Protestants.
Fr. Pavel Florensky