Short answers, pulled from the story.
Xunzi, born Xun Kuang around 310 BCE in the state of Zhao, is ranked as the third great Confucian philosopher of antiquity after Confucius and Mencius. He produced a thorough revision of Confucianism that synthesized Taoist and Mohist critiques with earlier Confucian thought, and his work was crucial to the philosophy's ability to flourish in the Han dynasty and across the later history of East Asia.
Xunzi argued that human nature is evil, using the Chinese term è (惡) to describe humanity's inborn tendencies as a dangerous starting condition. He believed this nature could not be overcome but could be transformed through education, ritual, and disciplined practice, which he called artifice (偽). This placed him in direct contrast with Mencius, who held that human nature is intrinsically good.
Xunzi studied at the Jixia Academy in the state of Qi, established by King Xuan and considered the most important philosophical center in ancient China. He traveled between age 13 and 15, around 297-295 BCE. He later returned to the academy as a highly regarded teacher, eventually becoming its head, and composed many of his most important philosophical works there.
Xunzi's most famous students were Han Fei and Li Si, both of whom had important political and academic careers. Li Si became Chancellor of the Qin dynasty. Their Legalist inclinations were at odds with Xunzi's Confucian philosophy, and Li Si's association with Qin's authoritarian rule later tarnished Xunzi's reputation.
Repeated oversimplifications and misunderstandings of Xunzi's teachings, particularly his view that human nature is evil, led to his gradual dismissal and condemnation from the Tang dynasty onward. By the rise of Neo-Confucianism in the 10th century, Mencius had displaced him, a shift reinforced by the decision to include the Mencius in the Four Books while leaving Xunzi out.
In chapter 20, the Discourse on Music (Yuelun; 樂論), Xunzi argued against the Mohist philosopher Mozi, who dismissed music as a waste of resources. Xunzi held that certain music produces joy, which is essential to human wellbeing, and that music fosters social harmony. Both music and joy share the same Chinese written character, 樂, a connection Xunzi used to support his argument.