The Catholic Church is the oldest institution in the western world, and with more than one billion members worldwide, it is the largest Christian church. Its history spans almost 2,000 years and is rooted in the Church's Canon of Scripture and Tradition. At the head of the church is the Pope, who Catholics believe is the successor to Saint Peter whom Christ appointed as the first head of His church. The Pope, according to the religion's doctrine, can speak infallibly on matters of faith and morals. The Catholic Church practises closed communion and only baptised members of the church are permitted to receive the Eucharist, or Holy Communion.