Baba Kama 87a - Blind People and Mitzvos

Tosafos (here, and kiddushin and rosh hashana) writes that even according to R' Yehuda that blind people are exempt from mitzvos, that is on a d'oraysa level, but m'drabonon they are chayev in mitzvos. Although women who are patur from time bound mitzvos are even patur on a d'rabonon level, Tosafos assumes that by a blind person the rabbonon would have definitely been mechayev them in mitzvos - סומא אי פטרת ליה מכל המצות אפילו מדרבנן, אם כן הוה ליה כמו נכרי שאין נוהג בתורת ישראל כלל

The argument is that a woman still has some mitzvos that she is chayev in, but if a blind person is exempt from mitzvos, there is no noticeable difference in behavior between him and a goy, so chazal would have been mechayev him in mitzvos. Clearly, this argument is only applicable to a blind person. Chazal never entertained being mechayev a deaf person or fool in mitzvos m'drabonon, because their exemption is attributed to a lack of da'as, whereas a blind person according to r' yehuda who is not exempt due to a lack of da'as rather a gezeiras hakasuv, it is logical for chazal to be mechayev them.

The Nodeh B'yehuda (tinyana, o.c. 112) quotes the pri megadim (psicha o.c. 29) who says that even according to r' yehuda a blind person is chayev m'doraysa in negative commandments, he is only exempt from mitzvah aseh. The Nodeh B'yehuda says that the language of Tosafos implies that he is like a goy and would be entirely exempt from everything. Although the pesukim imply that a blind person is completely exempt from everything, the diyuk from tosafos isn't so strong (mahartz chiyus also makes this diyuk). Ultimately the Nodah B'yehuda is medayek from the subtle language of Tosafos in various places. In Baba kama he says that the language of אין נוהג בתורת ישראל כלל implies an exemption even from lo ta'aseh. But the language of Tosafos in Rosh hashana 34a דאינו נוהג כישראל כלל can be understood like the pri megadim, because even if he abstains from prohibitions, he is still not being "noheig ki'yisrael" without any positive commandments.

The Nodah B'yehuda suggests that if a blind person is exempt even from lo ta'aseh he would not be able to make a bracha on mitzvos aseh that the rabbonon imposed on him since he is exempt from "lo tasur" (which according to the gemara in shabbos is the source for being able to make brachos on rabbinic mitzvos). But if he is obligated in lo ta'aseh, then after the rabbonon obligate him in positive mitzvos, he is able to make a bracha on them. However, one can make an argument that since other jews can make brachos, even one who is not obligated in a mitzvah and performs them can also make brachos. Tosafos in kiddushin 31a proves that women make a bracha on mitzvos they are exempt from, from the fact that a blind person makes brachos on positive mitzvos. What is the proof, perhaps a blind person can make a bracha since he is rabbinically obligated whereas a woman isn't even obligated rabbinically? The Nodeh B'yehuda explains that if we assume blind people are patur from lo ta'aseh, they too should not be able to make a bracha even if they are rabbinically obligated in the aseh. From the fact that they do proves that one can make a bracha even when the obligation doesn't apply to them, therefore women can also make a bracha.