Born in 1873 in Dublin, Moriarty spent his early adulthood traveling in the merchant services. He eventually settled in Mossel Bay, South Africa. In 1897, he was initiated as a Freemason.
He returned to England in 1916 and became a teacher of “Universal Theosophy.” It is around this time he began to mentor Dion Fortune. She based her practice of trance mediumship on his techniques. Six years later she published fictional stories based on his teachings. The character she based on him was Dr. Taverner. These stories were later collected in “The Secrets of Dr. Taverner,” which is still in print.