From the Roman Catholic Daily Missal, 1962:
Among the truths which faith teaches us, there are several which all ought to know and believe explicitly, namely, the existence of God; the Mystery of the Holy Trinity; the Mystery of the Redemption of mankind by the Incarnation and death of Jesus Christ, and the future state of reward and punishment.
There are things which every Catholic is also bound to know by the express command either of God or of the Church. These things are: 1.) The three most ordinary Catholic prayers, namely, the Lord’s Prayer, the Hail Mary, and the Apostles’ Creed; and also, at least in substance, 2.) The Commandments of God; 3.) The Precepts of the Church; 4.) The Doctrine of the Sacraments, and especially of these three which are necessary to everyone, namely, Baptism, Penance, and the Holy Eucharist; 5.) The duties and obligations of one’s state in life.
It is a mortal sin for a Catholic to be ignorant of these things, if it be through his own willfulness or neglect.