Here’s Christopher Hitchens:

The great thing about writing a book is that it brings you into contact with people whose opinions you should have canvassed before you ever pressed pen to paper. They write to you. They telephone you. They come to your bookstore events and give you things to read that you should have read already. It’s this dialectical process that makes me glad I chose the profession I did: a free education that goes on for a lifetime.

(Quoted in the “Teach What You Know” chapter of Show Your Work!)