This essay starts from a question: Why are Conrad’s works so enduring and far reaching? A basic Confucian concept, Cheng (诚, sincerity), seems to offer a ready answer to this question. According to The Doctrine of the Mean (中庸, one of The Four Books), “entire sincerity is ceaseless,” meaning if a person possesses absolute sincerity, his influence will be long lasting and far reaching. This essay demonstrates that sincerity is one of Conrad’s essential personal traits, which serves as a guiding principle in his treatment of human relationships and his aesthetic handling of art. First it attempts to remove the two doubts hanging over Conrad’s sincerity as an author and as a friend—his obscurity and his duplicity. It then exposes deeper affinities between Conrad’s sincerity and the Confucian Cheng, to see how they tackle the following questions: How is sincerity defined? What is the role of sincerity in the universe? And how important is sincerity for human relationships? Finally, this essay concludes that sincerity, for Conrad, means singleness of mind; it is the foundation of artistic endeavor and forms the basis of human solidarity, through which one achieves the meaning of being.