In 1963 Fr. William entered St. Joseph's Abbey in Spencer, Massachusetts. While there he developed a contemplative prayer method based on the 14th-century classic treatise The Cloud of Unknowing. It has led to a prayer method called Centering Prayer. Fr. William moved from St. Joseph's Abbey to St. Benedict's Monastery in 1979, where he has served as prior and novice director. His books include works on various religious themes, including a commentary on The Cloud of Unknowing. He gives retreats, lectures and workshops on centering prayer, forgiveness, and the enneagram in the US and abroad.