Daf 15. Summary. Rabbi Yohanan lists the steps toward accepting the yoke of heaven: relieve yourself, wash your hands, lay on tefillin, recite Shema, and pray.
Mishnah. One who recites Shema softly so that he does not hear himself has fulfilled the obligation, but not according to Rabbi Yosei. One who did not enunciate clearly fulfills the obligation according to Rabbi Yosei, but not according to Rabbi Yehuda. One who recited Shema out of sequence did not fulfill the obligation.
Gemara. Must we recite audibly because the text says Shema! (hear)? Does hear mean literally that one must hear, or that one may recite in any language that will be understood? How would the command to hear apply to a deaf person? If the obligation to recite has been fulfilled in practice but would have been ruled invalid theoretically, is it nevertheless fulfilled?
Comment. The case of the one who cannot hear, whether because he prays softly or is deaf, is disputed at great length. It remains unclear (at least to me) whose opinions permit that which they don’t encourage and whose opinions are stringent. Rabbi Tavi said that Rabbi Yoshiya said that the halakha is to be lenient, but the gemara goes on to cite examples where ambiguities in the text are not resolved that may lead to stricter interpretation. The intense need for certainty is confounded by a lack of clarity as to the origin of the teachings that are being parsed. The daf ends in the middle of a sentence.