My favorite person in Deaf History is William Stokoe. At first, I was going to go with Geronimo Cardano because being the first to do something takes conviction and courage. However, turning preconceived notions on their head, I think, is even harder.
When learning to read, teachers are always urging you to “sound it out”. But if you can’t hear, that’s not an option. I can understand where the Oralism proponents are coming from, not being able to do things as other do them can make it tough to function in society. So the thought that deaf people should be taught to talk is a well-meaning, but ultimately flawed, proposal. Yet that was what the majority of people got behind, until Mr. Stokoe came along.
It takes a strong belief in not only yourself but also in that which you’re advocating for to propose something that flies in the face of conventional wisdom. Thankfully. Mr. Stokoe had both. By proving, not just claiming, that sign language is a valid language, he gave deaf (and hard of hearing) people everywhere a chance to succeed. He leveled the playing field. It is far easier for hearing people to learn a deaf language than deaf people to learn a hearing language.