John Cacioppo says that loneliness is a signal as fundamental to our well-being as hunger and thirst. Robert Kull chose to live completely alone off the coast of Chile for a year. Bill Friskics-Warren conducts a quick trip through some classic songs of loneliness. Thomas Dumm thinks a lonely society can be a dangerous one. Kathleen Norris describes Acedia, a kind of frantic escapism and aversion to other people.