Just as a person who ate forbidden fat twice in one spell of unawareness is liable to only one hatat, so too, when the transgression is in doubt, he is liable to only one asham talui. If in the meantime he became aware [of the possible sin] he is liable to a separate asham talui for each act, just as he would [in similar circumstances] be liable to a separate hatat for each act. Just as one is liable to separate hatats if he ate, in one spell of unawareness, forbidden fat and blood and piggul and notar, so, too, when the transgression is in doubt, he is liable to an asham talui for each different act. [If both] forbidden fat and notar lay before a person and he ate one of them but does not know which; Or if his menstruant wife and his sister were with him in his house and he has sex unwittingly with one of them and does not know with which, Or if Shabbat and Yom Kippur [followed each other] and he did forbidden work at twilight and does not know on which day: Rabbi Eliezer declares him liable to a hatat; But Rabbi Joshua exempts him. Rabbi Yose said: they did not dispute about a person that did work at twilight, for he is certainly exempt, for I may assume that part of the work was done on the one day and part on the following day. About what did they dispute? About one who did work during the day itself but he did not know whether he did it on Shabbat or on Yom Kippur, or if he did work and did not know what manner of work he did: Rabbi Eliezer declares him liable to a hatat; But Rabbi Joshua exempts him. Rabbi Judah said: Rabbi Joshua exempts him even from an asham talui.