Why do people withdraw from life, sometimes for long periods? Guy Stagg poses this question in relation to three of the most arresting figures of the 20th century: the transformative philosopher Ludwig Wittgenstein, the remarkable poet and painter David Jones and the intellectual and mystic Simone Weil.

In this intriguing book, Stagg identifies a number of reasons why these three figures pursued such radically different lives from most of us. Some of them are easy to understand. All three were essentially loners. Furthermore, solitude provided the means to concentrate on essential work: Wittgenstein went to a remote area of Norway in order to write the Tractatus Logico-­Philosophicus; Jones spent the last years of his life in a dishevelled hotel bedroom giving himself over totally to painting and lettering. 

But some of the motives that drove this apartness are more startling. For Weil, it was a desire to fully understand human suffering. This was what led her to work for six months on a factory floor, despite being nearly crippled by migraines, and to travel to Spain to join