I agree with this. It's not infrequently that I feel I have a clear idea of something, only to try writing it out and discover that I don't. Most of us here ha

I agree with this. It's not infrequently that I feel I have a clear idea of something, only to try writing it out and discover that I don't. Most of us here have heard the story about Feynman, when he decided that if he couldn't explain a concept clearly enough for undergrads, it meant that he didn't really understand it himself.