He taught not only those doctrines of Judaism which appertained to the Law, but also those portions of the Holy Scriptures which had no direct bearing on the Law. He gave lectures on the writings of the prophets and historians in the form of discourses, which had for some time past been in use both in and out of the synagogue. These lectures were either edifying, comforting, or bitter, sharp, and ironical, and applied the words of the prophets about Edom and Esau, to hated Rome and its tyranny. This kind of exposition of Scripture had a name, "Agada" or "Hagadah." Its chief subjects consisted in explaining historical events, prophetic utterances, and in bringing to mind the past, and treating of the future of Judaism. The Agada investigated the meaning of the Law, examined into the general moral truths of Judaism, deftly united the present with the past, and shadowed the present conditions of life in past experiences. The Halacha forms the chief trunk of the Law, the Midrash the suckling roots, which drew their nourishment from the words of Scripture. The Talmud formed the wide-spreading branches, and the Agada was the blossom which scented and colored the simple fabric of the laws. In his Agadic dissertations Jochanan endeavored to illuminate the ordinances of the Law by the light of the understanding, and to combine them into general truths, but in a clear and simple manner, utterly dissimilar from the exaggerated method of the Alexandrian-Jewish teachers, who endeavored to extract the dazzling light of the Grecian mode of thought from Holy Writ. Amongst other things, Jochanan explained very quaintly why the use of iron is forbidden in erecting an altar. Iron is the symbol of war and dissension; the altar, on the contrary, is the symbol of peace and atonement; therefore iron must be kept away from the altar. He deduced therefrom the high value of peace, the advantages of peace between man and wife, between one city and another, and between one nation and another. These were the principles which had induced him to side with the Romans against the revolutionaries. In this way he explained various laws, and rendered them comprehensible, when they seemed obscure or in any way extraordinary. Jochanan was wont to hold converse also with Pagans who had knowledge of the Jewish Law, either from the Greek translation or from their intercourse with the Jews, refuting the objections which they raised, and dispelling or making clear by suitable comparisons the peculiarities which occur in the Holy Writings.