Solidarity as a phenomenon lies like an erratic block in the midst of the moral landscape of our age. Until now, the geologists familiar with this landscape, such as ethicists and moral theorists, have taken it for granted and have circumnavigated it in any case. They have also, however, been incapable of moving it. In the present volume, scientists from diverse disciplines discuss and examine the concept of solidarity, its history, its scope and its limits.