In the fourth part of the series, Diarmaid MacCulloch makes sense of the Reformation, and of how a faith based on obedience and authority gave birth to one based on individual conscience. He shows how Martin Luther wrote hymns to teach people the message of the Bible, and how a tasty sausage became the rallying cry for Swiss Reformer Ulrich Zwingli to tear down statues of saints, allow married clergy and deny that communion bread and wine were the body and blood of Christ.

Dawkins opines that the moral framework of religions is warped, and argues against the religious indoctrination of children. He discusses specifically the idea of religion seen as a virus in the sense of a meme. He begins by explaining how a child is genetically programmed to believe without questioning the word of authority figures, especially parents – the evolutionary imperative being that no child would survive by adopting a sceptical attitude towards everything their elders said. But this same imperative, he claims, leaves children open to infection by religion.

In the third episode of the series, Morgan Freeman examines different faiths' concepts of God, discovering how monotheism began in Egypt and Israel and allowing a neuroscientist to examine his own brain.

With optional Hebrew subtitles. Simon Schama's history of the Jewish experience plunges into the lost world of the shtetl, the Jewish towns and villages sewn across the hinterlands of Eastern Europe which became the seedbed of a uniquely Jewish culture. Shtetl culture would make its mark on the modern world, from the revolutionary politics of the Soviet Union to the mass culture of Tin Pan Alley and Hollywood. It was also the birthplaces of Hasidism, the most visible, iconic and, arguably, most misunderstood expression of Jewish faith and fervour. This chapter of the story travels from the forests of Lithuania, where Simon's own family logged wood and fought wolves, to the streets of the Lower East Side where the sons of shtetl immigrants wrote the American songbook. With grim inevitability, the story returns to Eastern Europe in 1940 - where the genocidal mechanisms of the 'final solution' were beginning to grind the shtetl world into dust and ash.

Diarmaid MacCulloch's own life story makes him a symbol of a distinctive feature about Western Christianity - scepticism, a tendency to doubt which has transformed both Western culture and Christianity. In the final programme in the series, he asks where that change came from. He challenges the simplistic notion that faith in Christianity has steadily ebbed away before the relentless advance of science, reason and progress, and shows instead how the tide of faith perversely flows back in. Despite the attacks of Newton, Voltaire, the French Revolutionaries and Darwin, Christianity has shown a remarkable resilience. The greatest damage to Christianity was actually inflicted to its moral credibility by the two great wars of the 20th century and by its entanglement with Fascism and Nazism. And yet it is during crisis that the Church has rediscovered deep and enduring truths about itself, which may even be a clue to its future.

Diarmaid MacCulloch traces the growth of an exuberant expression of faith that has spread across the globe - Evangelical Protestantism. Today, it is associated with conservative politics, but the whole story is distinctly more unexpected. It is easily forgotten that the evangelical explosion has been driven by a concern for social justice and the claim that one could stand in a direct emotional relationship with God. It allowed the Protestant faith to burst its boundaries from its homeland in Europe. In America, its preachers marketed Christianity with all the flair and swashbuckling enterprise of American commerce. In Africa, it converted much of the continent by adapting to local traditions, and now it is expanding into Asia. But is Korean Pentecostalism and its message of prosperity in the here and now an adaptation too far?