Pope Benedict XVI's sudden resignation announced on Monday marks an extraordinary end to a paradoxical papacy. Timid yet outspoken, the Pope helped reshape global Christianity around an intellectual revival that favours close engagement with other world religions, above all Islam.
His near eight-year reign has been enmeshed in turmoil, linked notably to the child abuse scandals and his contentious stance on contraception and HIV. Benedict's papacy has also been dogged by the recent whistle-blowing "Vatileaks" scandal in which his erstwhile personal butler leaked private letters and confidential documents.
However, since his selection in April 2005, the Pope has rarely ceased to surprise the world with his interventions. Contrary to the arch-conservative image, his positions transcend the conservative-liberal divide, especially on economic and social issues as well as interfaith dialogue.
On the latter, Benedict is undoubtedly best remembered for his controversial 2006 Regensburg address, in which he appeared to equate Islam with violence (he quoted a Byzantine emperor who said some of the teachings of the Prophet Mohammed were "evil"). But in reality, he used much of that address to condemn violence in all religions, saying hatred and conflict in the name of belief are a perverse distortion of true faith.
The seemingly inflammatory nature of his Regensburg remarks sparked violent protests across the wider Middle East and Pakistan. Faced with angry reactions, Benedict apologised for any offence caused and said that the "true meaning of my address was and is an invitation to frank and sincere dialogue, with mutual respect".
The kind of interfaith engagement he championed represents a clear break with the past 50 years of largely meaningless rhetoric about how all faiths are essentially the same and how Jews, Christians and Muslims all pray to the same divinity. But since Islam does not consider Jesus Christ to be the Son of God and Christianity does not view Mohammed on the same par as the prophets of the Old Testament, it is no good pretending that each is simply a variant of the other.
On the contrary, mutual understanding and reciprocal respect require that Christians and Muslims recognise and debate fundamental differences that distinguish their respective faiths. Such an approach is at once traditional and progressive.
Thus, for Pope Benedict, the best hope for genuine peace and tolerance between Christianity and Islam is to have a proper religious engagement about the nature of peace and justice. Otherwise, interfaith dialogue among believers will amount to little more than the polite platitudes of politicians and diplomats. Based on their shared commitment to truth and wisdom, Christians and Muslims should have debates that are theologically informed and politically frank.
The fundamentalists on each side will only be intellectually defeated and effectively marginalised by reasoned belief and rational argument about what true religion might be and how to practise it within each faith tradition - not the illusion of sameness across different creeds that denies each their own distinctness.
Likewise Pope Benedict's appeal to true faith was a powerful argument against secular extremists and militant atheists who dominate discourse on religious belief. They need to be challenged when wrongly claiming that all religions are inherently violent and that only the privatisation of faith will rid the world of conflict and evil.
As such, the Pope sought to chart an alternative vision beyond both religious fanaticism and secular radicalism. His vision remains one of the most ambitious attempts to revive religion intellectually and to underscore its enduring importance in both politics and culture, nationally as well as globally.
For these reasons, his theological-political legacy is of tremendous significance for all world religions, especially Christianity and Islam. But these ideas also apply to Hindu nationalism and Islamic fanaticism in global hot spots - from the Indo-Pakistani dispute to the contested region of Kashmir.
Pope Benedict's social teaching resonates strongly with people of all faiths, and of none. From the outset he argued that the world economic crisis has revealed a deeper crisis of public morality and private integrity. For 30 years, executive culture and global finance have separated corporate risk from private reward and making money from doing good.
The effect of this aggressively self-serving approach have been catastrophic, locking many parts of the world in a vicious circle of debt and demoralisation.
Beyond the standard response of either more bureaucratic state regulation or more cut-throat free-market competition, Pope Benedict called for much stricter limits on the power of national states and global markets which converge and undermine both community and society. His vision of a "civil economy" seeks to embed contracts in relationships of trust and cooperation on which vibrant economies depend.
Last year, the Vatican published a series of proposals to transform the world economy. These proposals combine stricter laws on corruption and a small tax on speculative financial transactions with a system of rewards for more virtuous behaviour. For example, company law could be rewritten to reflect not just shareholder value but also the environment and society by introducing green technology or building social housing. Beyond the liberal-conservative divide, Pope Benedict's position is economically egalitarian and politically pragmatic.
Of course all this requires the mobilisation of people around the globe. But Benedict's ideas are more prescient and radical than the secular ideologies of left and right. His legacy cannot be dismissed as simply conservative or purely religious.
Adrian Pabst is lecturer in politics at the University of Kent and editor of The Crisis of Global Capitalism: Pope Benedict XVI's social encyclical and the future of political economy