Our Lord reserved to Himself certain things which He would do in due time in a manner outside the course and order of nature, so that they would wonder and be astonished at seeing not great but unusual things, who are unmoved by things daily seen. For the government of the world is a greater miracle than feeding five thousand men from five loaves; yet at the former no one wonders, the latter astonishes all men: not as a greater wonder, but as a rarer.
Saint AugustineAs to those other things which we hold on the authority, not of Scripture, but of tradition, and which are observed throughout the whole world, it may be understood that they are held as approved and instituted either by the apostles themselves, or by plenary Councils, whose authority in the Church is most useful, e.g. the annual commemoration, by special solemnities, of the Lord's passion, resurrection, and ascension, and of the descent of the Holy Spirit from heaven, and whatever else is in like manner observed by the whole Church wherever it has been established.
Saint Augustine