sentences:  In 643, when Emperor Taizong's son crown prince Li Chengqian was discovered to plot to overthrow Emperor Taizong, Emperor Taizong deposed him.Initially, Emperor Taizong considered making his favorite son Li Tai the Prince of Wei crown prince instead—a suggestion that Liu and Cen Wenben concurred in—but later, after deciding that Li Tai's scheming was responsible for Li Chengqian's downfall by making Li Chengqian insecure about his position, Emperor Taizong created another son, Li Zhi the Prince of Jin crown prince instead.After Li Zhi became crown prince, Liu pointed out that the crown prince should be often near righteous individuals so that he could learn how to act from them.