Before continuing to make the case for Judeo-Christian values, it is time to answer a question frequently posed by Jews and Christians as well as others: How can there be such a thing as Judeo-Christian values when Judaism and Christianity have different, sometimes mutually exclusive, beliefs?
The most important answer is that beliefs and values are not the same things.
Of course, Judaism and Christianity have some differing beliefs. If they had the same beliefs, they would be the same religion. The very term "Judeo-Christian" implies that the two are not the same. The two religions have some differing beliefs and occasionally even some different values.
For example, Christianity believes in a Trinity that Judaism does not believe in. That is a major theological difference, but it has no impact on values. Likewise, Christianity believes that the Messiah has come, whereas Judaism believes that he has not yet come. As a Jewish theologian, I am fascinated by theological differences among religions. But I am far more preoccupied with real-life issues of good and evil, and that is where Judeo-Christian values come in.
Both religions are based on the Old Testament, which Judaism and Christianity hold to be divine or divinely inspired. Clearly, then, they will share values -- unless one holds that the New Testament rejects Old Testament values. But that is untenable since, in addition to Christianity believing the Old Testament is God's word, Jesus was a believing and practicing Jew. He would not practice a religion whose values or Bible he rejected.
One way to understand Judeo-Christian values, therefore, is as values that emanate from a Judeo-based Christianity. Christians have always had the choice to reject the Jewish roots of Christianity (which, when done, enabled Christian anti-Semitism), to ignore those roots, or to celebrate and embrace them. American Christians have, more than any other Christian group, opted for the latter.
For much of Christian history, the majority of Christians either ignored or denied the Jewish origins of Christianity and the Jewishness of Jesus and the Apostles. That is how many Christians were able to rationalize their anti-Semitism, and that is why Europe self-identified as "Christian," not as "Judeo-Christian" as America has.
It is also true that as the centuries passed, some values differences, not merely theological ones, did arise. But it is the greatness of Judeo-Christian values that they combine the best of both religious traditions and cast aside some of their weaker aspects.
For example, the Christian emphasis on faith above works led often to faith without works. Meanwhile, the Jewish emphasis on works above faith has led to many Jews abandoning God and valuing only works -- meaning, more often than not, the embracing of destructive secular radical faiths.
Judeo-Christian values combine the two religions' strengths -- the Jewish emphasis on moral works in this world with the Christian emphasis on keeping God at the center of one's values and works.
Another example is the American Christian's ability to remain God-centered and hold onto traditional beliefs while fully participating in modern society. This has not generally been the case in Jewish life. Over the centuries, God-centered and Torah-believing Jews retreated from mainstream society. They did so because: 1) anti-Semitism forced Jews into ghettos; 2) Jewish ritual laws increasingly restricted contact with non-Jews; and 3) Jews are a people, not just a religious group.
On the other hand, Jewish rituals have kept Judaism and the Jews alive while the abandonment of ritual (for example, Sabbath observance) has hurt Christianity. And Jewish peoplehood has ensured action on behalf of persecuted fellow Jews while Christians usually did little on behalf of persecuted fellow Christians -- as, for example, those many Christians terribly persecuted under Communism; the Copts in Egypt; the Maronite Catholics in Lebanon; and the Christians of Sudan.
In sum, despite whatever differences they have, Jews and Christians need each other and Judaism and Christianity need each other. The Judeo-Christian values system has become a uniquely powerful moral force. Among its many achievements is that it is the primary contributor to America's greatness.