To become Jewish, there are three main requirements. They are: 1. Acceptance of the divine commandments, 2. Circumcision (in the case of a male only), and 3. Immersion in a ritual bath. Traditional Judaism requires all three of men, and the first and third of women. There is no wiggle room, any element missing invalidates the conversion.
I will not elaborate about those movements that seek to perform conversions without the necessary elements. Such "conversions" are clearly of no use. A ceremony, no matter how nice it is, and no matter how beautiful the certificate, is not a valid conversion according to traditional Judaism. There must be acceptance of Jewish religious observance, circumcision for the man and immersion in the ritual bath for all.
It is on the first element that the controversy rages. How does one define acceptance of the divine commandments? Is it an ultra-Orthodox interpretation? Perhaps merely desiring to identify as a Jew should be enough.
It is fascinating how unique Judaism is among the religions of the world! Not only does Judaism avoid proselytizing, rabbis will actively dissuade potential converts from joining the religion. Contrast that with Christianity and Islam, which both actively seek converts. At some point in history, they did so at the point of a sword. Islam still does this, wherever it can.
Why would Judaism push away potential converts? Shouldn't we expect a religion with so few people to seek to expand its numbers, and thus gain more influence in the world? If Judaism believes itself to be the true religion, why shouldn't it welcome converts?
The answer is, Judaism does welcome converts, as long as they are sincere. And, here is a crucial difference with other religions. Judaism does not require someone to be Jewish in order to be "saved." All that is required is adherence to the seven laws of the sons of Noah, the basis for universal morality. They include not killing, stealing, committing sexual immorality, idolatry, blasphemy, consuming the flesh of a living animal, and a requirement to establish a system of justice.
That's it, that's all that is required. All humans who obey the seven rules have a portion in "the world to come," and find great favor in God's eyes. There is no need to convert to Judaism. In truth, there is a very strong argument NOT to convert to Judaism.
Judaism requires 613 commandments. That's a lot more than seven. Once a person becomes Jewish, that is how intense their required religious observance is. Failing to observe those commandments is a sin, and thus we do not encourage non-Jews to accept that responsibility. It's not doing someone a favor to encourage them to accept responsibility without being completely certain that they are prepared to do so. Once the accept the responsibility, and fulfill it, then their reward is certainly great!
For this reason, traditional rabbis discourage potential converts until such time as they are convinced of their sincerity. If the potential converts keeps coming back, and insists that they wish to join the Jewish religion, then they are encouraged to study the details of the 613 commandments and Jewish religious observance.
Thus, the first requirement of acceptance of the commandments, is meant to protect the soul of the potential converts. We want to make sure they are prepared to fulfill this awesome responsibility. Without this acceptance, there is no basis for conversion.
Now, many wish to convert for reasons other than religion. They may wish to convert for marriage, for Israeli citizenship, or for social reasons. If a person wishes to convert solely for the purpose of marriage or practical reasons, and has no intention of observing Judaism, such a conversion is a tragedy. (Born Jews who are not observant are a separate discussion).
Conversion is a responsibility, not a right. To inter-dating couples, who are considering conversion for the non-Jewish partner, I strongly urge you to avoid nontraditional conversions. While they may alleviate an immediate family pressure situation, such conversions will not be recognized by all branches of Judaism. Should your children become involved with partners from a more traditional background, they may face a very difficult situation when their Jewish status is questioned.
I am not urging you to break up the relationship, but rather consider the consequences. I am urging you to learn about traditional Jewish observance, and consider a sincere conversion which will lead you to living a Jewish life. If that does not interest you, I suggest keeping the status quo and making it clear that one partner is not Jewish. If that partner is the woman, the children will be considered non-Jewish and will need to convert authentically should they wish to change that status. It is your free choice, and should be taken with all due consideration.
Within the realm of acceptance of the commandments there is some disagreement as well. My personal opinion is that the "big three" of Sabbath observance, Kashrut observance, and family laws including mikva, are the absolute minimum. Once the potential convert has agreed to observe these laws, as a starting point, I believe they should be welcomed. More orthodox people may require more of a total commitment. My feeling is that a sincere commitment to the basics is worth much more than a total commitment that may not be as sincere, but rather simply to "get the rabbinate off my case."
Conversion is a highly respected act, involving self-sacrifice and commitment. It should not be any less, and to eradicate the core of commitment is to render it a meaningless, social gesture. Inter-dating couples do not need to convert, if they do not intend to lead observant Jewish lives. Simply to do so in an inadequate ceremony, to assuage the guilt of some Jewish parent, is dishonest at best.
All branches of Judaism should recognize the time honored requirements of conversion, and thus preserved Jewish unity and the core commitment that has enabled Jewish survival throughout the centuries.