Weapons and armor are a country's tools of violence. A warlike country, however huge and safe it may be, will end up declining and endangering its populace. Military force cannot be entirely eliminated nor used all the time. Teach people military arts when they are free from farming in order to equip them with a sense of military decorum and morale. . . . Confucius said, "Not teaching people how to fight is the same as discarding them." Hence military might serves to benefit the realm. This is the gist of the art of war. Review the passage, then answer the question.

Why does Taizong use a quote from Confucius to support his argument? Explain your answer in one or two sentences.