Two periods of special sanctity light up Judaism’s ritual year like bonfires at opposite ends of the globe, one starting with the New Year in the fall and the other with Passover in the spring.

Passover begins this Monday evening. It is a celebration of freedom, of God’s deliverance and of our gratitude for God’s gift of the family. On Passover, families gather to celebrate a ritual in which parents teach their children to remember and be faithful to their history.

This apotheosis of the family makes a thought-provoking background for a decision announced last Monday by the Jewish Theological Seminary. Henceforth the seminary will accept openly gay students at its rabbinical school. This decision is a tragedy not only for “Conservative” Judaism, which sponsors the seminary, but also for Jews everywhere.

Why is the decision tragic?

Because there are many roles to which we are each fitted, and many that are not appropriate for us. “You aren’t eligible for this role” is just bigotry talking and ought to be disregarded. In other cases, role requirements reflect reality. The essence of adulthood is knowing the difference — and accepting the fact that you are not meant for every part, no matter how much you wish you were. This is a matter of qualifications, not rights.

I would have had fun being a Hollywood star, but I don’t qualify. Chances are you don’t either. Judaism tells us to make the most of ourselves, to “choose life,” and enjoy the gorgeous poetry of God’s universe. It proclaims that we are all equal in God’s eyes, and are only required to do our best.

“God says to Israel,” the rabbis tell us, “I told you to pray to me in your synagogues; but if you cannot, then pray in your house; and if you cannot do that, pray in your field; and if this is hard for you, pray in your bed; and if you cannot even do that, think of Me in your heart.” Do what you can. God understands. That is Judaism’s view — the view of normative, rabbinic, “orthodox” Judaism.

But consider the case of a Jew who openly refuses to keep kosher, and loves ham sandwiches. In this respect he is not a good Jew — but he might be a good human being.

A Jew is required to keep God’s commandments, but might be unwilling or unable to keep them all. God understands and urges us each to repent — or in Hebrew, return — until our dying moments. The prophet Ezekiel writes, “Have I any pleasure at all that the wicked should die? saith the Lord God; and not that he should return from his ways, and live?”

The Jew who publicly proclaims his love for ham sandwiches might be a wonderful person; might be a much better man than I. But he is the wrong man to be the rabbi at any kind of synagogue — Orthodox, Conservative, or Reform.

A rabbi is a teacher and must do his best to show us how a Jew should live. We don’t expect our rabbis to be perfect, but we do expect them to do their best to show the way. A rabbi is like an officer in the Israeli army — he is expected to lead his men into battle and to say, “Follow me!”

In Judaism a man is incomplete until he finds a bride; a woman is incomplete until she finds a bridegroom. The Zohar, the classic medieval work of Jewish mysticism, explains, with italics added by the author: “Anywhere male and female are not found together, the Holy One Blessed Be He does not abide there. Blessings are found nowhere but in a place where male and female are found, as it is said [in Genesis]: ‘He blessed them and called their name Adam on the day they were created.’ It is not said, ‘He blessed him and called his name Adam’ — for man is not so called except when male and female are one.” A man must have a wife, a woman must have a husband to be complete. Otherwise he or she is only part of a human being.

We are told that a homosexual can’t help it. So the openly gay rabbinical candidate is saying, in effect: “I have an urge to commit homosexual acts, which I can’t or won’t suppress.” Another candidate might be a married man with an urge to commit adultery. If our two urge-ridden candidates suppress their urges, or at least don’t parade them in public, they might make acceptable rabbis. Otherwise, they should find another line of work.

In the Talmud we learn that only three sins justify Jewish martyrdom: idolatry, murder, and illicit sexual relations. Those sins are the worst of all. If open homosexuals are welcomed to the pulpit, no one is barred. And we learn, at last, what it means to live in a world where nothing is sacred.

Mr. Gelernter, a national fellow at the American Enterprise Institute, is a professor of computer science at Yale University and author of a forthcoming book on Jewish theology.