Gee writes “while you can teach someone linguistics, a body of knowledge, you can not teach them to be a linguist”. This means you can give someone a guide to act or perform like a linguist but in order for them to become a linguist, they have to do it themselves. “Discourses are not bodies of knowledge like physics or archeology or linguistics”. For example, you can give someone a book about basketball and they can learn the rules and understand the game but for them to become a basketball player, they need to play basketball.
