On All Saints' Day, the Pope told members of the Italian Catholic Action youth organisation that the Penny Catechism was the basis on which everything else was built. St. Augustine, St. ThOmas Aquinas, and all the other doctors of the Church studied the catechism and built their towering concepts upon it.
The study of the catechism forms one of the essentials of Catholic Action, which, to quote the encyclicals, is " to learn in order to teach; to improve oneself in order to improve others."
