The question: Can religion save the world?The debate about whether "religion" or "secularism" stands the best chance of alleviating 21st-century political conflicts will continue to be mired in debilitating confusion unless we are clear what people mean when they speak of a "secular state" (or a "secular international order").First, a state may be called secular if it is officially committed to a secularist faith such as atheism or materialism or secular humanism and to propagating it through state action. This is "militant secularism", the kind witnessed under Communism. Second, a state may be deemed secular if, while upholding private religious liberty, it strives to keep the influence of religious faith out of public debate and public institutions. This is "exclusive secularism", the variety defended by the National Secular Society. Third, a state may be termed secular if it refrains from officially endorsing any one religious creed, adopting a stance of impartiality towards all. This is "impartial secularism"; it flows out of the logic of religious toleration. Fourth, a state may be thought of as secular if it refrains from officially offering religious justifications for its laws or policies, presenting to the public only "public good arguments". This is "justificatory secularism". While impartial secularism is a matter of what the state does (or refrains from doing) towards religious citizens, justificatory secularism is a matter of how it speaks about what it does. My central proposition is that religion stands the best chance of mitigating political conflict if it embraces the latter two meanings of a secular state and a secular international political order. Above all, religion should support impartial secularism, urging the state to grant effective equal legal standing to all (law-abiding) religions within its realm. The suppression of religious freedom will continue to be a chief cause of violent political conflict in the century ahead, and those states that engage in it, notably officially Islamic states, must face ceaseless pressure from defenders of impartial secularism everywhere. Impartial secularism can exist without justificatory secularism, and departures from the latter are less inherently politically divisive than breaches of the former. But where states officially invoke religious justifications for their actions they risk alienating those of their citizens who cannot endorse such justifications. Justificatory secularism on the part of the state can engender a sense of equal respect among all citizens and so help pre-empt or ease religiously-based political divisions. But it is essential to insist that justificatory secularism does not imply exclusive secularism. For states and state officials to refrain from officially invoking religious arguments in support of state actions is entirely compatible with protecting an extensive and intensive contribution from religious faith to public debate both outside and inside parliaments, right up to the point of the official announcement of a policy decision. While we should call upon states to respect justificatory secularism, we cannot impose a similar restraint on the justifying reasons advanced by citizens or their elected representatives. That would have silenced Desmond Tutu in his campaign against apartheid. Allowing freer reign for religious expression may make democratic debate more turbulent. It may make secularist and religious believers uncomfortable. It will certainly require everyone to bone up on the religious (or secularist) beliefs of those they find themselves debating with. Tony Blair's attempt to create greater religious awareness among school children thus seems eminently sensible and NSS's opposition to it leaves me scratching my head since I thought it favoured banishing ignorance. It is a chief error of many secularist believers to suppose that impartial secularism implies exclusive secularism, that the state cannot treat religions equally unless public policy debates are secularised. This is both a prejudicial and a dangerous error. Its consequence is the marginalisation of those citizens for whom religious faith is both the deepest and the most comprehensive source of normative guidance. Exclusive secularism is therefore both illiberal and anti-democratic and is guaranteed to fuel existing religious tensions or evoke latent ones. The track record of conflict-resolution through imposed public secularism is, to say the least, unimpressive, as the case of Turkey makes clear. Religion will neither be the dominant source of 21st-century political conflicts nor the unique solution to them. But religions, and political orders, which embrace impartial and justificatory secularism while rejecting militant and exclusive secularism may be well placed to help mitigate them.