In this final episode of the series, professor Diarmaid MacCulloch explores how the offical Christian Church and Western society have moved apart on issues of sex and gender over the last 300 years. The Enlightenment encouraged people to question authority and that included the Church's teachings on sex. In the late 17th century, prostitution and homosexuality openly flourished in western cities - an open affront to centuries of Christian teaching. At the same time, new forms of Protestantism, such as Methodism, began to question traditional Church teaching, giving leadership roles to women.

In the Victorian age, sex became a subject for scientists to study, instead of a sin for the Church to condemn. Some Christian thinkers began to challenge the sexual status quo. Josephine Butler fought on behalf of prostitutes, while Bishop John Colenso argued that African converts should be allowed to continue their practice of polygamy. And in the mid 20th century, Christians were at the forefront of the successful campaign for the decriminalisation of homosexuality. But elsewhere, Church leaders railed against these changes. Rome insisted on no divorce, no homosexuality, no contraception. And in recent years, both Catholic and Protestant Churches have been mired in sex abuse scandals. Does Christian thinking still have anything to teach a secular world about sex?