In the Middle Ages rabbis were forced to engage with priests in disputations in the presence of kings and cardinals on which is the true religion, Judaism or Christianity. The outcome was predetermined. Christians won; they had the swords. But in the post-WW II era, disputations gave way to the conviction that the two religions say the same thing and the differences between them are dismissed as trivial. Now a new kind of disputation has begun, in which the truth of the two religions is subject to debate. That marks a return to the old disputations, with their intense seriousness about religious truth and their willingness to ask tough questions and engage with the answers. My book, A Rabbi Talks with Jesus, was one such contemporary exercise of disputation, and now, in 2007, the pope in his new book Jesus of Nazareth in detail has met the challenge point-by-point. Just imagine my amazement when I heard that a Christian reply is fully exposed in Pope Benedict XVI's reply to A Rabbi Talks with Jesus in his Jesus of Nazareth Chapter Four, on the sermon on the Mount. POPES INVOLVED in Judeo-Christian theological dialogue? In ancient and medieval times disputations concerning propositions of religious truth defined the purpose of dialogue between religions, particularly Judaism and Christianity. Judaism made its case vigorously, amassing rigorous arguments built upon the facts of Scripture common to both parties to the debate. Imaginary narratives, such as Judah Halevi's Kuzari, constructed a dialogue among Judaism, Christianity, and Islam, a dialogue conducted by a king who sought the true religion for his kingdom. Judaism won the disputation before the king of the Khazars, at least in Judah Halevi's formulation. But Christianity no less aggressively sought debate-partners, confident of the outcome of the confrontation. Such debates attested to the common faith of both parties in the integrity of reason and in the facticity of shared Scriptures. Disputation went out of style when religions lost their confidence in the power of reason to establish theological truth. Then, as in Lessing's Nathan the Wise, religions were made to affirm a truth in common, and the differences between religions were dismissed as trivial and unimportant. An American president was quoted as saying, "It doesn't matter what you believe as long as you're a good man." Then disputations between religions lost their urgency. The heritage of the Enlightenment with its indifference to the truth-claims of religion fostered religious toleration and reciprocal respect in place of religious confrontation and claims to know God. Religions emerged as obstacles to the good order of society. For the past two centuries Judeo-Christian dialogue served as the medium of a politics of social conciliation, not religious inquiry into the convictions of the other. Negotiation took the place of debate, and to lay claim upon truth in behalf of one's own religion violated the rules good conduct. In A Rabbi Talks with Jesus I undertook to take seriously the claim of Jesus to fulfill the Torah and weigh that claim in the balance against the teachings of other rabbis - a colloquium of sages of the Torah. I explain in a very straightforward and unapologetic way why, if I had been in the Land of Israel in the first century and present at the Sermon on the Mount, I would not have joined the circle of Jesus's disciples. I would have dissented, I hope courteously, I am sure with solid reason and argument and fact. If I heard what he said in the Sermon on the Mount, for good and substantive reasons I would not have become one of his disciples. That is difficult for people to imagine, since it is hard to think of words more deeply etched into our civilization and its deepest affirmations than the teachings of the Sermon on the Mount and other pronouncements of Jesus. But, then, it also is hard to imagine hearing those words for the first time, as something surprising and demanding, not as mere clich s of culture. That is precisely what I propose to do in my conversation with Jesus: listen and argue. To hear religious teachings as if for the first time and to respond to them in surprise and wonder - that is the reward of religious disputation in our own day. I WROTE the book to shed some light on why, while Christians believe in Jesus Christ and the good news of his rule in the kingdom of Heaven, Jews believe in the Torah of Moses and form on earth and in their own flesh God's kingdom of priests and the holy people. And that belief requires faithful Jews to enter a dissent from the teachings of Jesus, on the grounds that those teachings at important points contradict the Torah. Where Jesus diverges from the revelation by God to Moses at Mount Sinai that is the Torah, he is wrong, and Moses is right. In setting forth the grounds to this unapologetic dissent, I mean to foster religious dialogue among believers, Christian and Jewish alike. For a long time, Jews have praised Jesus as a rabbi, a Jew like us really; but to Christian faith in Jesus Christ, that affirmation is monumentally irrelevant. And for their part, Christians have praised Judaism as the religion from which Jesus came, and to us, that is hardly a vivid compliment. We have avoided meeting head-on the points of substantial difference between us, not only in response to the person and claims of Jesus, but especially, in addressing his teachings. He claimed to reform and to improve, "You have heard it said... but I say...." We maintain, and I argued in my book, that the Torah was and is perfect and beyond improvement, and the Judaism built upon the Torah and the prophets and writings, the originally-oral parts of the Torah written down in the Mishna, Talmud, and Midrash - that Judaism was and remains God's will for humanity. By that criterion I propose to set forth a Jewish dissent from some important teachings of Jesus. It is a gesture of respect for Christians and honor for their faith. For we can argue only if we take one another seriously. But we can enter into dialogue only if we honor both ourselves and the other. In my imaginary disputation I treat Jesus with respect, but I also mean to argue with him about things he says. WHAT'S AT stake here? If I succeed in creating a vivid portrait of the dispute, Christians see the choices Jesus made and will find renewal for their faith in Jesus Christ - but also respect Judaism. I underscore the choices both Judaism and Christianity confront in the shared Scriptures. Christians will understand Christianity when they acknowledge the choices it has made, and so too Jews, Judaism. I mean to explain to Christians why I believe in Judaism, and that ought to help Christians identify the critical convictions that bring them to church every Sunday. Jews will strengthen their commitment to the Torah of Moses - but also respect Christianity. I want Jews to understand why Judaism demands assent - "the All-Merciful seeks the heart," "the Torah was given only to purify the human heart." Both Jews and Christians should find in A Rabbi Talks with Jesus the reason to affirm, because each party will locate there the very points on which the difference between Judaism and Christianity rests. What makes me so certain of that outcome? Because I believe, when each side understands in the same way the issues that divide the two, and both with solid reason affirm their respective truths, then all may love and worship God in peace - knowing that it really is the one and the same God whom together they serve - in difference. So it is a religious book about religious difference: an argument about God. WHEN MY publisher asked for suggestions of colleagues to be asked to recommend the book, I suggested Chief Rabbi Jonathan Sacks and Cardinal Joseph Ratzinger. Rabbi Sacks had long impressed me by his astute and well-crafted theological writings, the leading contemporary apologist for Judaism. I had admired Cardinal Ratzinger's writings on the historical Jesus and had written to him to say so. He replied and we exchanged offprints and books. His willingness to confront the issues of truth, not just the politics of doctrine, struck me as courageous and constructive. But now His Holiness has taken a step further and has answered my critique in a creative exercise of exegesis and theology. In his Jesus of Nazareth the Judeo-Christian disputation enters a new age. We are able to meet one another in a forthright exercise of reason and criticism. The challenges of Sinai bring us together for the renewal of a 2,000 year old tradition of religious debate in the service of God's truth. Someone once called me the most contentious person he had ever known. Now I have met my match. Pope Benedict XVI is another truth-seeker. We are in for interesting times. The writer is distinguished service professor of the history and theology of Judaism at Bard College, Annandale-on-Hudson, New York.