Knoweth this man letters - The Jewish letters or science consisted in the knowledge of their Scriptures and traditions. Jesus exhibited in his discourses such a profound acquaintance with the Old Testament as to excite their amazement and admiration.
Having never learned - The Jews taught their law and tradition in celebrated schools. As Jesus had not been instructed in those schools, they were amazed at his learning. What early human teaching the Saviour had we have no means of ascertaining, further than that it was customary for the Jews to teach their children to read the Scriptures. 2 Timothy 3:15; “from a child thou (Timothy) hast known the holy scriptures.”