Recent theoretical discussions of optimism as an inherent aspect of human nature converge with empirical investigations of optimism as an individual difference to show that optimism can be a highly beneficial psychological characteristic linked to good mood, perseverance, achievement, and physical health. Questions remain about optimism as a research topic and more generally as a societal value. Is the meaning of optimism richer than its current conceptualization in cognitive terms? Are optimism and pessimism mutually exclusive? What is the relationship between optimism and reality, and what are the costs of optimistic beliefs that prove to be wrong? How can optimism be cultivated? How does optimism play itself out across different cultures? Optimism promises to be one of the important topics of interest to positive social science, as long as it is approached in an even-handed way.