Isaiah Berlin was one of the greatest thinkers of the 20th century – a man who set ideas on fire. His defence of liberty and plurality was passionate and persuasive and inspired a generation. His ideas – especially his reasoned rejection of excessive certainty and political despotism – have become even more prescient and vital today. But who was the man behind such influential views? Henry Hardy, Berlin’s decades-long editor and collaborator, offers an intimate and revealing picture of the self-deprecating philosopher.