This book contains the historic lectures given on the first five principles of the Ten Principles of Happy Science from the author, Ryuho Okawa, who is revered as World Teacher. He established Happy Science in October 1986, and built Head Temples, local temples, and missionary centers around the world, with members in more than 160 countries around the globe. These first five lectures produced an enthusiastic fellowship in Happy Science Japan and became the foundation of the current global utopian movement. It starts with the historic lecture, The Principle of Happiness, in which Okawa delivered The Fourfold Path of Love, Wisdom, Self-Reflection and Progress, a universal method to attain true happiness for all people revealed to the world for the first time. In this book, you can learn the essence of Okawa's teachings and the secret behind the rapid growth of the Happy Science movement in simple language. By reading this book and implementing the Exploration of the Right Mind in your life, you will come to know that your essence is that of a spiritual being and learn that the mind is the only thing you can take back to the other world or afterlife. Also, by living the Fourfold Path of Love, Wisdom, Self-Reflection and Progress, you will attain true happiness and start on your path to enlightenment. These principles serve to integrate all religion, philosophy, and academic study.