Rav Yehudah citing Rav: The Halachah follows R. Eliezer (in the Mishnah above - see 74-1) (c)).

Question: What is the reasoning of the Chachamim who disagree with him?

R. Yirmiyah citing R. Shmuel bar Rav Yitzchak: The pasuk states (Devarim 23, 3), "A Mamzer shall not enter the congregation of Hashem'' - he may not enter a certain congregation but he may enter a doubtful congregation.

Mishnah in Maseches Yevamos: (If a man did yibum and then discovered that his yevamah is pregnant) - the child is either a 9th month child from the first husband or a 7th month child from the yavam. They must separate, child is Kasher and they must bring an Asham Talui offering (since it is unclear whether they transgressed the prohibition of relations between a brother and sister in law when there is no Mitzvah of yibum).

Beraisa: (If they did not divorce and they had a second child) The first child is Kasher to be a Kohen and the second is a doubtful Mamzer.

R. Eliezer ben Yaakov: There is no prohibition for a doubtful Mamzer to marry a regular Jew.

R. Eliezer ben Yaakov agrees that a doubtful Kusi and a doubtful Chalal may not marry a regular Jew or a Kohen, as the Torah only permitted a doubtful Mamzer, as the Mishnah taught earlier, that ten categories of genealogy ascended from Bavel (including Shtuki and Asufi). According to R. Eliezer ben Yaakov there were 8 categories (as Shtuki and Asufi may marry). According to Rabban Gamliel and R. Elazar there were 9 categories (as Shtuki is Baduki, that can marry). According to the Rabbanan, there were 10 categories.