In the 18th century, Diderot, the representative of the French Encyclopedic School, wrote La Mo's Nephew, which was regarded as the masterpiece of the school of metaphysics because it embodied the basic ideas of metaphysics, especially in describing the development of characters and the philosophical thinking of fate. The protagonist in " Ramo's Nephew " was a man with a complicated fate. He experienced many unfortunate things but finally got a happy ending. This kind of fate was consistent with the philosophical views that 'everything is relative' and 'change is eternal' emphasized by the dialect. Through Lamo's fate, the author deeply explored the essence of human existence and the meaning of fate, expressing the deep thinking of human fate in the field of metaphysics. In Rameau's Nephew, Diderot also used a lot of thoughts to explore the nature of society and human existence. For example, in his novel, he elaborated on the concepts of "contradiction" and "opposites" and believed that the development of human society was determined by the struggle between contradictions and opposites. This kind of philosophical thinking inspires us to understand the essence and development trend of human society. In summary, Ramo's Nephew, as Diderot's masterpiece, embodied the basic ideas of metaphysics and profoundly explored the nature of human existence and social development trends, so it was considered as the "masterpiece of metaphysics".