The Episcopal Church maintains that the Holy Scriptures are the ultimate rule of faith. Its symbols of doctrine are the Apostles' and the Nicene Creed and the Thirty-nine Articles of the Church of England, with certain modifications to fit American conditions. The ministry is of three orders: deacons, priests, and bishops. The system of organization includes the parish, the diocese, the province, and the General Convention. The General Convention, the highest ecclesiastical authority in the church, consists of the House of Bishops and the House of Deputies (which includes the clergy and laity) and meets in session every three years. The ecclesiastical head of the church is the presiding bishop, elected by the General Convention. The National Council, set up in 1919, is delegated by the General Convention to administer all the organized missionary, educational, and social work. The church has more 2.4 million members in the United States (2005).