The first resignation of a Pope in 600 years naturally caused shockwaves around the world.

Pope Benedict XVI simply decreed, as he approaches his 86th birthday, that he lacks both the physical and mental strength required to carry out the duties required of him. That very act, however, is a mark of the continuing strength of mind of the former Cardinal Josef Ratzinger, who was one of the oldest new popes when he was elected in 2005.

After less than eight years his legacy as supreme pontiff is a complex one. An eminent theologian who brought back the Latin mass, his orthodoxy and cleaving to fundamental values divided liberals and more fundamental Catholics.

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He saw stemming the tide of secularism as an important part of his role and underlined the importance of Christian values as a moral basis for life on his 2010 visit to Britain. That he began that first state visit by a Pope to the UK in Edinburgh made him warmly received in Scotland where 65,000 attended the mass at Bellahouston Park in Glasgow.

But Benedict XVI's papacy was dogged by a series of controversies. An uncompromising outspokenness on issues ranging from homosexuality and Aids to the Holocaust and Islam meant protests accompanied his pastoral visits and often led to international reverberations.

In 2006 his description of a mediaeval account of the teachings of the Prophet Muhammad as evil and inhuman provoked violent protests in several countries and he was forced to apologise. A remark that condoms aggravated Aids, made en route to Africa in 2009, was equally ill-judged. The greatest crisis was the church's handling of the revelations of child sexual abuse by priests in many countries and over many years.

As right-hand man to the charismatic John Paul II for 24 years and as head of the Congregation for the Doctrine of the Faith, he had been responsible for disciplining church dissidents and upheld church policy against liberal attempts at reform, earning himself the label of God's rottweiler. Although he has met survivors of clerical abuse and apologised to them, there remains a sense of betrayal among many that he failed to deliver what he had promised in terms of ensuring perpetrators were held to account.

Liberal Catholics feel the holding to fundamental values and the centralising of decisions in Rome have had a negative effect on the church. Recently the substantial leaking of documents from his office has pointed to a lack of control and a power struggle within the Vatican. It was perhaps significant that his resignation statement spoke of the demands of a fast-moving age. While the leader of the Catholic Church must define and defend the faith, and large numbers of Catholics have delighted in Pope Benedict's uncompromisingly robust statements, the social changes across the modern world cannot be ignored. Future popes may be expected to be infallible but they cannot turn back the tide of secularism simply by denouncing it.

Whoever the cardinals elect as the next supreme pontiff will need the communication skills of the 21st century as well as the age-old requirements of faith, knowledge and wisdom.