Gregory of Nyssa elaborated a theory of the stages of the mystical life that had a profound impact on the future of Christian spirituality. For Gregory, the spiritual journey is a dynamic adventure of progressively deeper union with God that can never stagnate or get boring, since our created nature can never contain or comprehend the fullness of the infinite God. Since God surpasses our intellect, Gregory identifies a certain darkness that characterizes the mystical experience, a theme that would be developed by many subsequent writers over the centuries.
— from the book When the Church Was Young: Voices of the Early Fathers
