In Origen we first find a great teacher who deliberately sets himself to the task of explaining Scripture. He became, at the early age of eighteen, the head of the catechetical school at Alexandria, an institution which not only trained catechumens but provided open lectures, on every part of Christian learning, and from that time to his death, at the age of sixty-nine, he was constantly engaged in the work of public exposition. At Alexandria his expositions took place in the school, but at Cæsarea they formed part of the church services, so that the reports of those belonging to the Cæsarean period provide us with the earliest examples we possess of the discourse at Christian meetings. In an activity which he practised so much Origen acquired extraordinary skill and facility, and gained the highest reputation, even beyond the limits of the Church. It is no wonder, therefore, if he succeeded in treating nearly the whole Bible in this way, a thing which might no doubt be said of many a Christian teacher since his day; for he was not one who was apt to repeat himself, but was constantly pressing on to break new ground.