"This book is intended no less for those who do sleep well than for those who do not. It is just as important to be able to teach others to act well as to be able to do so ourselves. To teach we must analyze and comprehend our own action and its motives: for being able to do a thing well is far different from being able to teach it. In order to teach anything we must know how we do it and why others cannot do it. We never know anything thoroughly...