In an early chapter of Ringworld, Speaker-to-Animals casually insults humanity and Luis Wu takes offense. Wu asks the Kzinti what the usual custom for such an insult is, and when he's told its a hand-to-hand duel to the death, he doesn't hesitate to issue such a challenge, knowing that he has no damned chance against a Kzin. One of the other Kzinti apologizes on behalf of Speaker-to-Animals, negating the need for the duel, and further explains that its his job to apologize for his race when Kzinti insult humans. Luis says, "I wouldn't have your job for nothing." The Kzinti looks Wu up and down and says, "Of course you wouldn't; not if you were willing to challenge a Kzin in a duel to a death." Thus validating Luis, and humanity, as a true Badass.