The Third Man Factor: Surviving the Impossible, By John Geiger

From the desolation of an Arctic winter to the exhaustion of a mind on the brink during university finals, John Geiger examines the extremes of human existence, both physical and psychological.

An experience common to those on the edge has been that of a benevolent, incorporeal force – what Geiger calls "the third man" – endowing them with the courage needed to pull through.

In his foreword, the Canadian physician Vincent Lam, who has travelled with Geiger, explains how, in his day job, he is used to assessing empirical reality – but knowing the "mechanics of the human body" has made him aware of the mysteries of human consciousness and thought.

This book is packed with tales from people as various as polar explorers and prisoners of war, and as well as appraising their experience of "the third man" – "profound geographic isolation", for instance, can lead to the distressing mental states of introversion and agitation – Geiger analyses the experience of venturing to places few have dared to go.