*124 Q. What do you mean by the infallibility of the Church? A. By the infallibility of the Church I mean that the Church cannot err when it teaches a doctrine of faith or morals. "Infallibility." When we say Church is infallible, we mean that it cannot make a mistake or err in what it teaches; that the Pope, the head of the Church, is infallible when he teaches ex cathedra--that is, as the successor of St. Peter, the vicar of Christ. Cathedra signifies a seat, ex stands for "out of"; therefore, ex cathedra means out of the chair or office of St. Peter, because chair is sometimes used for office. Thus we say the presidential chair is opposed to this or that, when we intend to say the president, or the one in that office, is opposed to it. The cathedral is the church in which the bishop usually officiates, so called on account of the bishop's cathedra, or throne, being in it. *125 Q. When does the Church teach infallibly? A. The Church teaches infallibly when it speaks through the Pope and bishops united in general council, or through the Pope alone when he proclaims to all the faithful a doctrine of faith or morals. But how will we know when the Pope speaks ex cathedra, when he is speaking daily to people from all parts of the world? To speak ex cathedra or infallibly, three things are required: (1) He must speak as the head of the whole Church, not as a private person; and in certain forms of words by which we know he is speaking ex cathedra. (2) What he says must hold good for the whole Church--that is, for all the faithful, and not merely for this or that particular person or country.