 At the age of fifteen he briefly followed his elder brother, Ngô Đình Thục, who would become Vietnam's highest-ranking Catholic bishop, into seminary.Diệm swore himself to celibacy to prove his devotion to his faith, but found monastic life too rigorous and decided not to pursue a clerical career.According to Moyar, Diệm's personality was too independent to adhere to the discipline of the Church, while Jarvis recalls Ngô Đình Thục's ironic observation that the Church was "too worldly" for Diệm.