APOSTLES CREED- IT IS WHAT ALL CATHOLICS SHOULD BELIEVE, MEMORIZE IT AND TEACH IT SINCE IT IS IN THE WORD OF GOD--Throughout the Middle Ages it was generally believed that the Apostles, on the day of Pentecost, while still under the direct inspiration of the Holy Ghost, composed our present Creed between them, each of the Apostles contributing one of the twelve articles more:: Apostles' Creed - The Catholic Encyclopedia - (studylight.org)