Zhang Zai was a prominent Chinese philosopher during the Song Dynasty, known for his contributions to Neo-Confucianism. Born in 1020, he emphasized the importance of moral cultivation and the interconnectedness of all things. His ideas focused on the unity of heaven, earth, and humanity, advocating for a harmonious relationship between individuals and the universe. Zhang Zai is best known for his work, the Zhengmeng, which outlines his philosophical views. He introduced concepts such as the "qi" (vital energy) and the "li" (principle), influencing later thinkers like Zhu Xi. His teachings continue to be studied and respected in Chinese philosophy today.