The Catholic Faith is not governed by shifting opinions and popular consent. The foundation of the Faith is revealed not only in the Person of Christ, but in the Teaching Authority given to the Church by Christ ("He who hears you, hears Me.")
There are three components of this foundation which we refer to as the "Deposit of Faith". The following three branches work in concert for continuity of teaching in the Church today and in the future:
Thus the Magisterium operates via two methods. The solemn or extraordinary Magisterium is seen in solemn definitions either by a pope, as for example, the definition of the dogma of the Assumption of Mary into Heaven in 1950, or by one of the Ecumenical Councils of the Catholic Church ratified by the pope, as the definitions made by the Council of Trent (1545-1563) to reaffirm the Catholic faith against the Protestants or the definition of papal infallibility by the First Vatican Council in 1870.
The ordinary and universal Magisterium, on the other hand, is the ordinary teaching of the Church, accomplished via papal pronouncements, statements of bishops, catechisms, homilies, etc. This is not to say that everything that any pope, bishop or priest has ever said on any occasion is part of the ordinary and universal Magisterium, but that it is via such means that this teaching is generally made known to the faithful. Note that the First Vatican Council speaks of it as both "ordinary and universal." "Ordinary" means that it is accomplished via the ordinary means of teaching that the Church uses, but "universal" means that it is taught by the entire body of bishops, and usually over a period of time. For generally when a doctrine has been taught as authoritative over time and by many popes and bishops, this indicates that it is a teaching of the ordinary and universal Magisterium and must be received and believed as faithfully as teaching that is solemnly defined by pope or council. (Emphases by Ed.)