How did the Saviour proceed in his preaching? We would expect to see him, as lawgiver and teacher, appearing with code of laws in hand, a complete body of doctrine embracing all the grand objectives he proposes. But he offers nothing of the kind: no text, no system, and nothing organised or presented according to any order whatsoever. He presents himself, and it is he who is the doctrine and the truth. He permits himself to be seen, and that is alreadly teaching; he acts, and that is teaching; he speaks, and the teaching becomes more precise, but without being fitted into the adapted framework of a system. His message exposes itself to the apparent chance of circumstances, and it is the ordinary environment of Jewish life that will be that of his apostolate….
What was true of his scene of action is therefore also true of the preaching itself. Jesus was not anxious to go everywhere; nor did he make a point of saying all there was to say, much less of saying it systematically. What has he to do with methods and systems? Why should he wish to express all things in one lump?…
The characteristics that distinguish the preaching of Jesus can be reduced to two: simplicity in depth and persuasive power resulting from the supernatural certitude of the speaker, of his character, and of his life.
Father Antonin Gilbert Sertillanges, O.P. +1948