An interrogation of why we don't talk to strangers, what happens when we do, and why it affects everything from the rise and fall of nations to personal health and wellbeing, in the tradition of Susan Cain's Quiet and Rutger Bregman's Humankind.

When was the last time you spoke to a stranger? In our cities, we stand in silent buses and tube carriages, barely acknowledging one another. Online, we retreat into silos and carefully curate who we interact with. But while we often fear strangers, or blame them for the ills of society, history and science show us that they are actually our solution. Throughout human history, our attitude to the stranger has determined the fate and wellbeing of both nations and individuals. A raft of new science confirms that the more we open ourselves up to encounters with those we don't know, the healthier we are.

In The Power of Strangers, with the help of sociologists, psychologists, neuroscientists, theologians, philosophers, political scientists and historians, Joe Keohane learns how we're wired to sometimes fear, distrust and even hate strangers, and discovers what happens to us when we indulge those biases. At the same time, he digs into a growing body of cutting-edge research on the surprising social and psychological benefits that come from talking to strangers; how even passing interactions can enhance empathy, happiness, and cognitive development, ease loneliness and isolation, and root us in the world, deepening our sense of belonging.

Warm, erudite and profound, this deeply researched book will make you reconsider how you perceive and approach strangers: paradoxically, strangers can help us become more fully ourselves.

Recent interest in the evolution of the social contract is extended by providing a throughly naturalistic, evolutionary account of the biological underpinnings of a social contract theory of morality. This social contract theory of morality (contractevolism) provides an evolutionary justification of the primacy of a moral principle of maximisation of the opportunities for evolutionary reproductive success (ERS), where maximising opportunities does not entail an obligation on individuals to choose to maximise their ERS. From that primary principle, the moral principles of inclusion, individual sovereignty (liberty) and equality can be derived. The implications of these principles, within contractevolism, are explored through an examination of patriarchy, individual sovereignty and copulatory choices, and overpopulation and extinction. Contractevolism is grounded in evolutionary dynamics that resulted in humans and human societies. The most important behavioural consequences of evolution to contractevolism are reciprocity, cooperation, empathy, and the most important cognitive consequences are reason and behavioural modification.

This book covers thirty years of the Leningrad Mathematical Olympiad, which was, ostensibly, the very first formally organized, open, official city-level mathematical contest in the world. Founded in 1934 by a group of dedicated Soviet mathematicians, it played an outstanding (and often underappreciated) role in creating the Leningrad (St. Petersburg) school of mathematics of the 20th century.The book begins with the extensive introduction containing two prefaces (one of them written specifically for this edition), a large historical survey of the Leningrad Mathematical Olympiad, a section describing the logistical side of the contest, and a small chapter dedicated to the very first Mathematical Olympiad held in 1934, whose problems were recently found in the Soviet-era library archives.The main text contains approximately 1,100 highly original questions for students of grades 5 through 10 (ages 11-12 through 17-18) offered at the two concluding rounds of the Leningrad City Mathematics Olympiads in the years of 1961-1991. Full solutions, hints and answers are provided for all questions with very rare exceptions.It also includes 120 additional questions, offered at the various mathematical contests held in Leningrad over the same thirty-year period — on average, their difficulty is somewhat higher than that of the regular Mathematical Olympiad problems.