I just started C. S. Lewis’ Mere Christianity and he explains in the preface that the book was originally a series of talks that he gave. Apparently in the first edition of the book he tried to maintain the conversational tone and leave the writing as close to the way he spoke as possible. Upon further reflection he decided to change that. He said:
A ‘talk’ on the radio should, I think, be as like real talk as possible, and should not sound like an essay being read aloud. In my talks I had therefore used all the contractions and colloquialisms I ordinarily use in conversation. In the printed version I reproduced this, putting don’t and we’ve for do not and we have. And wherever, in the talks, I had made the importance of a word clear by the emphasis of my voice, I printed it in italics. I am now inclined to think that this was a mistake—an undesirable hybrid between the art of speaking and the art of writing. A talker ought to use variations of voice for emphasis because his medium naturally lends itself to that method: but a writer ought not to use italics for the same purpose. He has his own, different, means of bringing out the key words and ought to use them. (Mere Christianity, vii)
I’ve never had a problem with italics for emphasis but Lewis raises an interesting point. A writer’s task is descriptive. The writer is supposed to make us see and hear and feel certain things through the use of the written word. Italics show emphasis but not necessarily the type of emphasis intended. A good writer will find a way to make the proper emphasis felt by allowing words to emphasize other words. This simple statement will revolutionize the way I read, and hopefully, the way I write.