Conversion is always a hot topic, especially here in Israel. Many times conversions take place where the person didn't have the intention to be makabel the mitzvos. People scream and shout, but seemingly the conversion (according to some) would be still be kosher!
The Rambam writes in Hilchos Issurei Bia Perek 13 Halacha 17:
גר שלא בדקו אחריו או שלא הודיעוהו המצות ועונשן ומל וטבל בפני ג' הדיוטות ה"ז גר. אפילו נודע שבשביל דבר הוא מתגייר הואיל ומל וטבל יצא מכלל העכו"ם וחוששין לו עד שיתבאר צדקותו. ואפילו חזר ועבד כו"ם הרי הוא כישראל מומר שקידושיו קידושין. ומצוה להחזיר אבידתו מאחר שטבל נעשה כישראל. ולפיכך קיימו שמשון ושלמה נשותיהן ואע"פ שנגלה סודן
Although this seems b'dieved clearly the Rambam holds that if the person did not know about the mitzvos (thus did not accept them) that they would still be considered a Jew.
The Bach writes in Yoreh Deah Siman 268 that according to the Rambam if the potential Ger wasn't makabel the mitzvos, "כשר אע"פ שלא היה לשם קבלת מצוות כל עיקר".
Although the Shulchan Aruch doesn't pasken like this l'halacha I'd like to know if there are any other Rishonim or earlier poskim that also held like this?
Yehoshua, Jerusalem, Israel
(a) The Teshuvos Chemdas Shlomo (YD 29-30) explains at length that Kabalas Mitzvos and Hoda'as Mitzvos are entirely different concepts.
1. The former is the brunt of Geirus; without it nothing that can be called Geirus. This is evident from the Rambam's very definition of Geirus, which he describes as follows:
כשירצה העכו"ם להכנס לברית ולהסתופף תחת כנפי השכינה ויקבל עליו עול תורה, צריך מילה וטבילה והרצאת קרבן (הלכות איסורי ביאה פרק יג הלכה ד)
Thus, without Kabalas Ol Torah, there is no Geirus to speak of. Such is clear from the Gemara in Bechoros 30b, which teaches that a Ger who refuses to accept upon himself even one minor, Rabbinic, teaching - is not accepted as a Ger. So much for Kabalas Mitzvos.
2. During the process of Geirus, we notify the Ger about certain specific Mitzvos while he is in the Mikvah. This is known as Hoda'as Mitzvos, and it is to that which the Rambam is referring to in Halachah 17. If Hoda'as Mitzvos in the Mikvah is not done, the Geirus can be Kosher b'Di'eved. But if a Ger converts with no intention of accepting upon himself the burden of Hash-m's Mitzvos, no conversion has taken place.
(It is interesting to note that even the Bach, who reads the Rambam as saying that Kabalas Mitzvos is not a necessary prerequisite for Geirus, argues with the Rambam in the same sentence.)
(b) Rav Chaim Ozer Grodzenski in Achiezer (3:26), cites the Chemdas Shlomo (and contests the Beis Yitzchak, who suggests that perhaps the Gemara in Bechoros is only discussing Geirus l'Chatchilah). Nevertheless, he makes a distinction between refusing to "accept" Mitzvos, and refusing to "adhere to" Mitzvos.
For example, if a Ger insists that he believes in every last letter of the Torah of Hash-m and His sages - but reveals that he does not have the willpower to overcome his cravings with regard to certain Mitzvos, his Geirus is valid. But if his actions show that he never took the Mitzvos seriously - his Geirus is not a Geirus at all.
I hope that clears the air a bit.
Best wishes,
Mordecai Kornfeld
Kollel Iyun Hadaf