Complex sentence: Religious experiences belonged to the "personal religion," which he considered to be "more fundamental than either theology or ecclesiasticism", and gave a Perennialist interpretation to religious experience, stating that this kind of experience is ultimately uniform in various traditions.
Split into simpler sentences: Religious experiences belonged to the "personal religion," which he considered to be "more fundamental than either theology or ecclesiasticism". He gave a Perennialist interpretation to religious experience, stating that this kind of experience is ultimately uniform in various traditions.