His parents were József Demén, a master tailor, and Mária Losigan. He entered the order on August 29, 1943. He took his first vows in Zirc on August 30, 1944. He likely left Hungary on October 24, 1948, in a railcar carrying bauxite in the Mosonmagyaróvár area. He took his final vows in Mehrerau, in the company of Henrik Marton and Boldizsár Szarka, in the presence of Balázs Fűz on March 21, 1949. He was ordained a priest in Innsbruck, Austria, on May 22, 1949, by Archbishop Josef Skvireckas of Kaunas. He arrived in the United States in 1951. He was one of the nine Hungarian founders of the Dallas Abbey. In 1958, he earned his doctorate in mathematics from Saint Louis University. In 1966, he requested a one-year leave of absence, and in March 1967, he requested his laicization. The Congregation for Religious, in its rescript No. 1136/68 dated March 14, 1969, reinstated him to lay status, at which time he joined the Unitarian Universalist Church. After leaving the order, he became a professor at Oklahoma State University (Stillwater).