In writing, the most important principle we teach, preach, urge, implore, and beg is: "Show it." Because he had a short section of telling, Mike assumed he had committed a literary sin. (He hadn’t.) Mike had learned to show and progressed to lesson two: It’s all right to tell--sometimes. In fact, good writing flows between showing and telling.
When do we tell?
You use telling statements to make value judgments. Maybe an example will help. I read an article in Publisher's Weekly that was informative and relevant.
Read that last sentence again. That’s an example of telling. I stated how I responded to one article. That is, I told readers how to think by citing two positive qualities. I made a simple declarative statement, but I wrote it as an indisputable (and unproven) fact. That defines telling—thinking for readers. At times, that’s acceptable and occasionally necessary.
Because good writing is subtle you need to learn to move between showing and telling readers.