John Opsopaus—often known by the name Apollonius—is a scholar, practitioner, and author whose work focuses on Paganism, classical magic, and systems of divination rooted in ancient Greek philosophical and mystical traditions. Opsopaus explores Neoplatonism, theurgy, sacred mathematics, and symbolic ritual practice, examining how ancient magical and divinatory methods were structured as disciplined spiritual sciences. His writings bridge historical scholarship and contemporary practice, presenting Pagan spirituality as an intellectually grounded tradition centered on harmony with cosmic order, ethical self-development, and philosophical understanding.