Whenever I have an article published in the international press, I get emails from Christians telling me how much they and Jesus love me, and wanting me to know how much better my life would be if only I could accept him as my savior. Alternatively, they ask me to explain those Biblical quotations they believe predict Jesus.
My usual reaction is to politely inform them that I have a direct line to God, thank you, and see no logical reason why I should need an intermediary--certainly not one who manifestly appears to have met neither his proclaimed goals nor those of any contemporaries who dreamed of messianic salvation. As for resorting to the Bible, the only concepts of messianism the Jews had were for a real-life king to return to power or else either a Divinely initiated state of world peace and universal ethics or a total change in the natural order. All of these we still await thousands of years later. And if the Biblical prophets referred to any human incarnations, they thought in terms of the proximate future, not hundreds of years ahead.
There is, of course, another response, which I only go into if I get a pigheaded refusal to take "no thank you" for an answer. I do not believe Jesus ever existed. To be more precise, the Jesus of Christianity is a mythical amalgam of ideas culled from Dead Sea sects dreaming of salvation, Pharisee popular preachers and folk healers, and anti-Roman political revolutionaries. The whole persona is a concoction culled from different sources, created to appeal to Roman pagans, and then modified to meet other traditions they wanted to impress. Essential Jewish messages were watered down or reworked to make them more accessible. A sort of popular, anodyne version of Judaism emerged to appeal to those who found the Hebrews too strict or too nationalist.
I have no gripe with popularists or reformers, particularly if they meet a clear need. But why should I go for a secondary version when the original still works perfectly well for me and makes more sense. As for someone having the insolence and the naivete to tell me that my relationship with my God, which underpins my life, is not good enough, I can only laugh and ask how in Heaven he or she can claim to know what only God can.
In truth, personalities play a far less important role in Judaism than does Torah itself. What matters to me is that direct covenant with God, reinforced by my own experiences which cannot be overruled by any prophet or miracle worker, just as miracles can have no impact on the Sinai Covenant. Being Jewish is a commitment to an ancient spiritual and a historical tradition that satisfies one's religious needs and aspirations.
Yehudah Halevy argued in Kuzari that other monotheistic religions emerged from Judaism so it makes sense to go back to the source. Nowadays, academics argue that Rabbinic Judaism is as much a creation out of Biblical Judaism as Christianity is. Arguably, what really forced them apart was the Christian decision in the fourth century to gain political power. To do so, they needed to assert their radical difference from Judaism and make sure they eradicated any internal heresies. Hence their passion for converting people according to their dogma that only they can be right and everyone else must be wrong. Christians actually killed off far more Christians for heresy than they did Jews. Just as nowadays more Muslims are killed by each other, in the Sunni versus Shia dispute, than by anyone else.
Daniel Boyarin (in Border Lines and other books) argues that it was very difficult to differentiate Jewish Christians from Christian Jews or other sects of Jewish origin during the first two hundred years after the destruction of the Temple. Jews and Christians then focused on heresy as the way to establish their separate identities. Since then, both parties have been constantly redefining heresy. In each era, a new set of criteria emerge to build on the past, and in the process create new fissures and subdivisions. Just think of the divisions in Christianity--Catholic, Orthodox, and Protestant, in all its varieties--and these are only the largest groups.
I object to Christian hypocrisy as much as I do to Jewish, but I deeply respect all humans regardless of religious affiliation and beliefs who are good caring human beings. If Judaism and Christianity were simply two variations on a religious theme, like, say, Catholicism and Protestantism, then switching would not be such a big deal. But the significance of Jesus is a major issue. Historically, it is associated in Jewish eyes with idolatry and undermining the purity of a non-material, non-human God. It came to represent the very Middle Eastern cults that Judaism distanced itself from. If, as our texts emphasize, God loves humanity despite our failings, why would we need anything more? And if Jesus IS God, then why add another concept, another name?
For a Jew, adopting another set of religious ideas, especially from one that has consistently tried to obliterate Jews or demean them, would require either persuasive ideas or some sort of escapism. Those Jews who do convert, usually have no deep experience of their own tradition (unless of course the conversion is in response to a political crisis, career advancement, or a partner). As for those who claim to be living religious Jewish lives but believe in Jesus as the Messiah, that seems to me to be just another variant of Christianity. Christianity is about Christ. If Christ is your redeemer, then that is where you belong. (And, no, it is not just the same as those Chabad Hassidim who think their dead rebbe is coming back, because they, and he, have never been associated with any breakaway.)
Judaism is a religion, but it is also much more. It includes the idea of a people, its history, its land, and its way of life, in addition to its faith. Different Jews emphasize different aspects. But certain religious traditions are so antithetical to the Jewish experience that, although one can feel close on a human level, adopting their religion makes no sense to the Jewish soul. Certainly there is room for variations on a messianic dream; but convert me to Jesus? You might as well get me to switch my allegiance from Manchester United to Charlton Athletic.