I believe Mark Twain is correct in saying that moral courage is a rare quality. In today's world, it takes courage to stand up for one's beliefs and values, especially when doing so means defying popular opinion or going against the grain of society. People often place a higher value on conformity and self-interest than on standing up for what is right. As a result, those with moral courage are often seen as exceptions to the rule, which can make them seem rare.