Can we ever really know the world? ... Debating the ideas of Thomas Kuhn, famous philosopher of science ... Will we ever see the end of war? ... Errol's book about Kuhn, The Ashtray: (Or the Man Who Denied Reality) ... Errol: Science without truth cannot live ... John sticks up for Kuhn ... Errol's vexed personal relationship with Kuhn ... Stephen Hawking's sense of humor ... Errol: "We're a dumbass species" ... The glass is half empty and filled with poison ...