Is conversion at all possible? This may sound like a rhetorical question since the answer is in the affirmative. Yet, this question goes to the very core of the institution of conversion, and as long as we do not deal with it, all deliberations concerning this matter are more or less meaningless. The reason for this is obvious: Logically speaking, conversion to Judaism should not be possible.
Just as it is impossible for a Jew whose father is not a kohen (priest) to become a kohen, similarly, it should be out of the question for a Gentile to become a Jew. Either one is born into a family of kohanim, or one is not. Presumably, then, either one is born a Jew, or one is not. God chose the Avot and their descendants as His people, and it is only they who can claim to be Jews. It would follow, then, that one is either part of this nation, or one is not.
Yet, conversion to Judaism is possible! How? It is the philosopher, Michael Wyschogrod (1928–2015) who, in his book The Body of Faith, gives an authoritative answer to this question: By means of a miracle.
A Gentile who converts to Judaism miraculously becomes part of the people of Israel. Unlike with Christianity, this does not just mean that the Gentile now shares the beliefs of Judaism, but rather that he or she literally becomes the seed of the Avot and Imahot. For this to happen, a quasi-biological miracle is required. The Gentile needs to be reborn as a direct descendant of Avraham and Sara. This is accomplished by immersion in a mikva, clearly symbolizing the mother’s womb through which one is born. The proof for this far-reaching conclusion is the fact that, according to the Torah, a convert is technically allowed to marry his or her own mother, father, brother, or sister. This may sound immoral, but for the profound, reflective thinker it is most telling and meaningful. The Torah views a convert as a completely new human being, recently (re)born with no biological attachments except to Avraham and Sara. This speaks volumes. It is true that the rabbis forbade converts to marry their close relatives, fearing that people might claim the Gentile gave up a stricter religion for one with more lenient rules of morality. But the fact that such marriages are rabbinically forbidden does not change the fact that they are biblically permitted.
This is radically different from baptism in Christianity. After baptism, the prohibition of incest is not waived. The biological relationship between parents and the baptized person continues as before. Not so in Judaism. What is required is the total rebirth of a person, as if new. While Jewish Law requires full respect for one’s biological, non-Jewish parents, it simultaneously makes it clear that conversion is an extreme step with radical consequences. That Judaism is prepared to make this step, against all logic, so as to allow a non-Jew to become, literally, a child of Avraham and Sara, shows it to be one of the most daring and open-minded religions. No non-Jew should be denied the possibility to join our nation when there is a sincere desire to do so, even when this very idea makes no sense.
For this reason, it is completely impossible to argue that mere immersion in a mikva is sufficient. It is crucial that the potential convert desire to become a different person and undergo a deeply spiritual transformation. Human beings are not just a mass of plasma, complicated robots, or tool-making animals who can change their fundamental selves simply by immersing in a well of water. They are souls, with deep emotions, who experience spiritual and moral struggles in which religious beliefs play a critical role. Therefore, conversion should be a well-thought-out decision, with an awareness of its implications, and rooted in the deepest recesses of the human soul. While this clearly includes the desire to become a part of the Jewish people, it is not enough. There is much more at stake.
The convert must become a follower of Avraham’s and Sara’s great legacy. This includes the acceptance of the Oneness of God, the need to be righteous, and the desire to inspire the world with the great moral foundations which were later solidified at Sinai. He or she must somehow embrace the great institutions of Judaism such as Shabbat, kashrut, and sexual dignity. Striving for kedusha/holiness and tahara/spiritual purity is of primary importance.
Whether or not the convert must a priori take on all the commandments, or only some, is a matter of great debate among the authorities. There are some who maintain that only a full kabbalat mitzvot (acceptance of the commandments) is sufficient. Anything less will not do. Others maintain that a sincere desire to be a part of the Jewish people is sufficient, though not ideal.
Why this difference of opinion about such a crucial and far-reaching issue?
Judaism and the Jewish people are intertwined and interact in ways which nobody can fully grasp. Are we a religion, or a nation? If we are a religion, how can it be that somebody who does not believe in God or refuses to observe even one commandment still remains Jewish as long as he or she is born to a Jewish mother? And if we are a nation, how does religion come in, telling us who belongs to the nation and who does not? Any attempt to find a solution to this problem will always fail, as it has in the past. There is no way to nail down these definitions. They elude us, and we must admit that we are confronted with one of the greatest mysteries of Jewish identity. We become aware of the existence of something we cannot penetrate.
It is for this reason that our authorities have different views on the question of conversion. Is one converting mainly into a religion, or mostly joining a nation? They realize that there is no completely satisfactory answer and have therefore been wise enough to somehow leave the question open.
Still, we must remember that without a strong religious component, conversion is a farce, just as it would be completely ridiculous to claim, conversely, that even though somebody is totally committed to all the mitzvot of the Torah and lives in its spirit, he or she would not be considered part of the Jewish people. He or she is, but we do not really know why or how. We need both components, religion and nationhood, but we cannot figure out how they relate to each other.
While caught in this strange mystery, however, we should neither make the mistake of thinking that only living by the laws of the Torah and Halacha and being part of the Jewish people is what is ideally required. Much more emphasis must be given to the great experience of being Jewish. There is something called a Jewish neshama (soul). Again, were we to try and define that, we may find ourselves accused of racial discrimination. Still, we all know the neshama is there. There is some built-in Jewish substance within us. Judaism is not only about nationhood and observance, but about living in a spiritual, emotional order which cannot be narrowed down to doctrines, dogmas, or commandments. It is important and necessary to emphasize this to someone who wants to convert. Halacha and beliefs are not enough. Somehow, he or she must inherit the great spirit of Avraham and Sara, which is more than the sum of all of the above parts, but also different from all the above. What it really is, we do not know. But it is! And how it transpires? Again, we do not know. But it happens. Again, it is a miracle wrought by God.
We can only ask that the convert accept all of this and initiate the climb up the “ladder of observance,” slowly but surely, combining nationhood with spiritual nobility.
Sounds paradoxical? Well, it is! Let it be, let it be. It has served us well through thousands of years and has made us into an eternal and indestructible nation. Let us not take this lightly.
 See Michael Wyschogrod, The Body of Faith: God in the People Israel (Northvale, NJ: Jason Aronson, 1996), xvi–xxi.
 See Yevamot 22a. This seems to oppose the rule (Kiddushin 78a and Mishne Torah, Hilchot Isurei Biah 18:3) that a kohen cannot marry a convert since she may have had sexual relations before she converted or because she comes from a (potentially) promiscuous background. It may be that this ruling came from a different talmudic tradition, or that the rabbis just felt that a woman from a (potentially) promiscuous background is not suitable to marry a priest. Halachic authorities need to examine this strange paradox more carefully and find a solution.
 See the conflicting statements in Bechorot 30b and Yevamot 47.
 A phrase coined by Abraham Joshua Heschel, The Insecurity of Freedom: Essays on Human Existence (NY: Farrar, Straus and Giroux, 1966), 206.