Quoted from the author's "Foreword."
"In my Key to Culture all the wonderful knowledge that the race now possesses is, in so far as every thoughtful man ought to know it, arranged in forty connected volumes. I call this the minimum of knowledge that a man needs in order to take an intelligent interest in the experiences of his life: in the life of his own body and mind, in the human family to which he and his nation belong and its social, economic and artistic activity, in the earth and its scenery and living inhabitants, in its relation to the universe of which it forms a part. Any man who has mastered those forty volumes, as many thousands have done, sees a new meaning in life as a whole and in most of the day's events, from a thunder-storm to a financial crisis or a political or religious conflict . But forty volumes are, after all, forty volumes, and when a man's job is done . . . In short, many have asked whether it would be possible to give a useful Outline of all this in one volume. Well, I think it is possible: that, in fact, the general view of the meaning of life and reality which is more important than the details can be seen and learned more clearly in one outline-book. It is a sort of key- to the Key for those who want to master that work thoroughly, and it brings the material up to date in such sections as astronomy, physics, prehistoric science, and early history. Others will find that it not only states in simple language some of the scientific theories or discoveries that are being discussed, but it leads up to these with elementary explanations. I have tried to tell all the most important truths of modern science and history but for men and women who have not made preliminary studies. Key-words or names or a few technical expressions which it is useful to remember are put in bold type. But I am hoping that all will see a useful service in this careful selection and organic arrangement of what is most important in modern knowledge."