Catechesis: What the Catechism Teaches

It [the Catechism] teaches what every Christian must know. So a person who does not know this catechism could not be counted as a Christian or be admitted to any Sacrament, just as a mechanic who does not understand the rules and customs of his trade is expelled and considered incapable. Therefore, we must have the young learn well and fluently the parts of the catechism or instruction for children, diligently exercise themselves in them, and keep busy with these parts.—LC Shorter Preface, 2