Paganism... is also a sort of permanent and natural magnetic pole of religion, and in this sense a constant threat for every religion. Christianity demands unceasing effort, continual filling of its forms with content, self-testing, and a "trial of the spirit". Any divergence between form and content, or the emergence of form as a value and goal in itself, is paganism. It is a return to natural religion, to belief in form, ceremony, and sacred objects without regard to their content and spiritual meaning. In this sense even Christian rites and sacred objects may themselves become centers of pagan veneration and may overshadow what they solely exist for: the liberating force of truth.
Alexander Schmemann, The Historical Road of Eastern Orthodoxy