Chagigah 3: Radical Empathy

On the list of people who are not obligated in the mitzvah of Re'eiah is the "deaf" person, a category which is expanded to include those who cannot hear but can speak, and those who can hear but are mute. How does their obligation differ from the obligation of others, including as that obligation is present in the mitzvah of Hakhel. Which spawns the question of whether those who cannot speak cannot learn. Also, a philosophy of learning, as found on this daf, that entails a different kind of hearing, namely, from the heart. Including how teachers learn from students, with an explicit focus on R. Elazar ben Azariah, and a cycling back to the mitzvah of Hakhel. Which leads into the absolute must of being able to hear others, even when you don't agree. A critical Gemara in understanding the purpose and implications of learning altogether.