The book explores how social cohesion can be established and demolished. Examples given are the US and UK, where social cohesion (measured as trust in unknown fellow citizens) declined in the latter part of the 20th century, and Sweden and Denmark, where social cohesion increased. The book provides a social constructivist explanation. It demonstrates the importance of public perceptions about living in a meritocratic middle class society. The decline in trust is explained by Americans and British developing the perception that most other citizens belong to an untrustworthy, undeserving and dangerous ‘bottom’ of society rather than to the trustworthy middle. In contrast, the increase in trust is explained by Swedes and Danes developing the opposite perceptions. The book argues that social cohesion is primarily a cognitive phenomenon - in contrast to previous research, which has emphasized the presence of shared moral norms, fair institutions, networks, engagement in civil society etc. The book is based on a unique empirical data material, where American survey items have been replicated in the British Social Attitude survey and the Danish and Swedish ISSP surveys (exclusively for this book). The book also includes a unique cross-national study of media content covering a five years period in UK, Sweden and Denmark. It demonstrates how ‘the bottom’ and ‘the middle’ is differently constructed across countries.