Carnegie Dale. The Art of Public Speaking

The efficiency of a book is like that of a man, in one important respect: its attitude toward its subject is the first source of its power. A book may be full of good ideas well expressed, but if its writer views his subject from the wrong angle even his excellent advice may prove to be ineffective.
This book stands or falls by its authors' attitude toward its subject. If the best way to teach oneself or others to speak effectively in public is to fill the mind with rules, and to set up fixed standards for the interpretation of thought, the utterance of language, the making of gestures, and all the rest, then this book will be limited in value to such stray ideas throughout its pages as may prove helpful to the reader—as an effort to enforce a group of principles it must be reckoned a failure, because it is then untrue.