He continued the work of his predecessor John XXIII by reconvening the Second Vatican Council (1963–65) of the Roman Catholic Church. Following the recommendations of the Council, he established important post-conciliar commissions. These investigated the need for reform of the liturgy and curia and ways to promote Christian unity and greater lay participation. A traditionalist by conviction, he was suspicious of any innovation that might undermine the authority of the Church, insisting on the necessity of priestly celibacy and condemning artificial methods of birth control.