Moral realism claims that moral facts exist independently of human thought. The chapter discusses moral skepticism and nihilism, which deny the existence of objective moral truths. It explores Mackie's arguments from relativity, queerness, and projection against moral realism. Harman's defense of extreme moral nihilism is presented, arguing morality is an illusion. However, criticism is made that scientific and moral observation are analogous, and moral claims can be tested, if not in the same way as empirical theories. The chapter concludes with an outline of a defense for moral realism based on facts about happiness and suffering.