Imagine sending a letter to a writer you admire and getting a personal reply packed with advice. Joan Lancaster didn’t have to imagine. In 1956, she became one of thousands of children who sent fan mail to C. S. Lewis, the author of The Chronicles of Narnia, and actually heard back.

Lewis’s charming letter encourages the aspiring young writer not to worry too much about grammar. “There are no right or wrong answers about language in the sense in which there are right and wrong answers in Arithmetic,” he writes. “Good English is whatever educated people talk; so that what is good in one place or time would not be so in another.”

He then adds a five-point list of what really matters:

1. Always try to use the language so as to make quite clear what you mean and make sure your sentence couldn’t mean anything else.

2. Always prefer the plain direct word to the long, vague one. Don’t implement promises, but keep them.

3. Never use abstract nouns when concrete ones will do. If you mean “More people died” don’t say “Mortality rose.”

4. In writing. Don’t use adjectives which merely tell us how you want us to feel about the thing you are describing. I mean, instead of telling us a thing was “terrible,” describe it so that we’ll be terrified. Don’t say it was “delightful”; make us say “delightful” when we’ve read the description. You see, all those words (horrifying, wonderful, hideous, exquisite) are only like saying to your readers, “Please will you do my job for me.”

5. Don’t use words too big for the subject. Don’t say “infinitely” when you mean “very”; otherwise you’ll have no word left when you want to talk about something really infinite.

Simple and spot on. Take them to heart and your writing will improve overnight. I promise.