This was written while Manning was still an Anglican and Archdeacon of Chichester. ST. AUGUSTIN, in his book concerning the instruction of persons ignorant of the Christian doctrine, after giving many rules for the guidance of the teacher, adds, "but if the catechumen be slow of understanding, and have neither hearing nor heart for the sweetness of truth, he must be borne with tenderly, and, after a short and cursory statement of other points, those things which are chiefly necessary are to be inculcated with much of awe, such as the Unity of the Catholic Church, the nature of temptation, and of the Christian life by reason of the judgment to come." It will sound strange to modern ears to hear the Unity of the Church thus numbered among the first principles of the doctrine of Christ; and by this we may measure how remote are our habits of thought from the tone of Catholic belief. It is to be noted, moreover, that St. Augustin does not treat the doctrine of unity as a first principle only, but as an elementary or axiomatic truth among the first principles of faith. It is to be taught to all catechumens, even to the least intelligent of them. It is, in fact, an object of faith, and a rule of life, without which no man call become a Catholic Christian. "Whatsoever any man may safely either not know at all, or know but ill part, this at least he must know thoroughly, and believe without a doubt.