This book deals with an important, though comparatively little known principle of Nature, and involves several facts of tremendous importance to the human race. Its basic truths were known to the ancients, and have also been stumbled upon by several modern teachers, but for the most part they have been distorted by reason of being attached to some weird, fantastic doctrine. Its teaching is advanced, but it is in no way contrary to the highest principles of conduct approved of by the best teachers of morality and religion.