I posted this in another thread in response to a question, but wanted to get some reactions from the members. IMO, while formal music theory training is not necessary, it allows you to progress further and faster, and I make this comparison. While you learn to speak your native language from listening to others, you still study grammar in school. Why? It allows us to speak and comprehend at a higher level, and learn more quickly. No one says you shouldn't study grammar in school, because it interferes with your "creativity". Neither should your study of music theory.