And what level of commitment to mitzvah observance does the court require as a precondition to conversion? “Even if the gentile commits to observing all the mitzvot except for one, we cannot convert him.” How do we square this statement with reality, wherein it is often transparent that the convert’s commitment to observe all mitzvot may be less than sincere?
The Achiezer differentiates between two types of potential converts. There is the convert who conditions his acceptance of the mitzvot on the exemption from one certain mitzvah. Then there is the convert who accepts all the mitzvot, even as he is dubious about his ability to observe them all. Whereas the conscientious objector is not a good candidate for conversion, the conscientious observer is, even though he, like the rest of us, is aware of the frailty of human determination. Rabbi Moshe Feinstein differentiates between before the fact and after the fact. A person who conditions his conversion before the court on an exemption from a certain mitzvah is not the right candidate for conversion. Nevertheless, if the court goes ahead and converts him, the conversion is valid and such a person, as a full-fledged Jew, must observe the mitzvah he spurned. Since nobody has the power to override a mitzvah, the condition is void.
The Tosafot Yeshanim suggests that any Jewish ambivalence toward conversion is perhaps rooted in the innate fear of being upstaged. Many converts are more conscientious in their observance of mitzvot than those who are born Jewish. Rather than allowing this to lead to the rejection of gerim, it should encourage those who are born Jewish to follow the example of the conscientious ger and increase their own commitment to mitzvot.