Professor Marc B. Shapiro blogs:
In fact, throughout most of Jewish history a lenient approach to conversion was the mainstream approach.
Now it is true that R. Herzog famously states that in earlier times one could be more lenient than today, because in a traditional society when someone converted he was immediately part of a community and was required to be observant.[22] Things are very different today when you can convert and move to a secular neighborhood in Tel Aviv. There is no communal pressure for you to be observant, and the convert can look around and see that the leaders of the Jewish people in Israel, Peres, Olmert and Livni, are not religious. In such a world, R. Herzog didn’t think we could rely on certain leniencies used in the past.
However, despite R. Herzog’s opinion, the lenient approach, which didn’t insist on a convert’s complete observance of mitvot remained popular in modern times. (Contrary to what has often been stated, the lenient approach, and this includes R. Uziel, always insisted on kabbalat mitzvot. The dispute concerns what "kabbalat mitzvot" means, and whether a formal acceptance, without inner conviction, is sufficient.) Until recent years the lenient approach was even a mainstream position, alongside the more stringent (and widespread) approach. Among the adherents of the lenient approach one must mention R. David Zvi Hoffmann, who was the final halakhic authority in Germany until his death in 1921. Almost every Orthodox rabbi in that country, and many in other parts of Western Europe, looked to him as their authority. Others who held this position include R. Unterman and R. Goren. In addition, the Israeli Chief Rabbinate batei din, which were full of haredi dayanim, until recently followed the lenient approach. Many non-Jews were converted in Israel by dayanim who knew perfectly well that these people were not going to live an Orthodox life. Some of them were even intent on marrying people who were living on secular kibbutzim.[23] No one ever challenged the validity of these conversions. The situation was similar in places outside of Israel.
…Unlike what goes on today, in previous generations there were never any classes for future converts. In fact, according to R. Akiva Eger, these classes are improper, since one is not permitted to teach Torah to a non-Jew.[24]
