Against the background of the historic visit of President Sadat to Jerusalem a year and a half earlier, and the treaty just negotiated under the aegis of President Carter, this discussion goes back and forth over the history, the current players, and the likely future. Mr. Katz is a hardliner who had just broken with his old associate (going back to Irgun days) Menachem Begin. Mr. Avineri has hopes for the treaty, partly because of Sadat's formal statement to the Knesset: " 'I am here to tell you that for thirty years we have not accepted you ... And here I am to tell you that we are now ready to live in peace with you and to accept you.' " In the course of their often sharp disagreements, Messrs. Katz and Avineri fill out our understanding of this explosive region.