This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book focuses on Sun Yat-sen's social, political, and economic ideas as seen in his major work, The Three Principles of the People, which discusses nationalism, democracy, and people's welfare. It analyzes Sun's life and time and the impact of traditional culture on his thought. The book examines the impact of Sun's doctrines on the future of China. It discusses Sun's Principles of the People. From June 1894 when Sun submitted a lengthy petition to Li Hung-chang, governor-general of Chihli, the nation's most influential statesman and a devoted champion of the reform movement, until Sun's death in March 1925, his idea of saving China underwent a process of evolution. The value of Sun's doctrine is assessed by three criteria: its originality, its consistency, and its relevancy to the contemporary world.