At the dawn of the new atheist movement, the thinkers who became known as “the four horsemen,” the heralds of religion's unraveling—Christopher Hitchens, Richard Dawkins, Sam Harris, and Daniel Dennett—sat down together over cocktails. What followed was a rigorous, pathbreaking, and enthralling exchange, which has been viewed millions of times since it was first posted on YouTube. This is intellectual inquiry at its best: exhilarating, funny, and unpredictable, sincere and probing, reminding us just how varied and colorful the threads of modern atheism are.

Here is the transcript of that conversation, in print for the first time, augmented by material from the living participants: Dawkins, Harris, and Dennett. These new essays, introduced by Stephen Fry, mark the evolution of their thinking and highlight particularly resonant aspects of this epic exchange. Each man contends with the most fundamental questions of human existence while challenging the others to articulate their own stance on God and religion, cultural criticism, spirituality, debate with people of faith, and the components of a truly ethical life.