Everyone is free in his belief. But the freedom of belief might divert and turn into heresies and heterodoxies that are exterior to the one faith of the Church. The Church, who has been alert over the faith to maintain it, does not allow this to happen nor does she give the authority of teaching to everyone, but examines the sayings of the teachers against the faith entrusted to the saints. Thus the saying of St. Paul the Apostle (Gal. 1:9) remains a fixed criterion.