CANBERRA – If we were hoping for peace in our time, 2012 did not deliver it. Conflict grew ever bloodier in Syria, continued to grind on in Afghanistan, and flared up periodically in West, Central, and East Africa. There were multiple episodes of ethnic, sectarian, and politically motivated violence in Myanmar (Burma), South Asia, and around the Middle East. Tensions between China and its neighbors have escalated in the South China Sea, and between China and Japan in the East China Sea. Concerns about North Korea’s and Iran’s nuclear programs remain unresolved.And yet, many feared eruptions within and between states did not occur. Strong international pressure helped to contain the Second Gaza War quickly. A long-sought peace agreement was secured for the southern Philippine island of Mindanao. Major strides were taken toward sustainable peace and reconciliation in Myanmar. There was no major new genocidal catastrophe. And, despite the United Nations Security Council’s paralysis over Syria, UN General Assembly member states made clear their continuing overwhelming acceptance of the responsibility to protect those at risk of mass-atrocity crimes.The bigger story has been concealed, as ever, by the media’s daily preoccupation with current bloodshed: Over the last two decades, major wars and episodes of mass violence worldwide have become much less frequent and deadly. After a high point in the late 1980’s and very early 1990’s, there has been a decline of well over 50% in the number of major conflicts both between and within states; in the number of genocidal and other mass atrocities; and in the number of people killed as a result of them.This "New Peace” phenomenon was first publicized by Andrew Mack’s Human Security Report Project, supported by the superb database of the Uppsala Conflict Data Program. Harvard’s Steven Pinker, in his seminal book The Better Angels of our Nature, put it in a larger historical context – not just the "Long Peace” between the major powers since 1945, but, more important, a centuries-old pattern of steady decline in the human appetite for violence.The many efforts that have been made to debunk this analysis (for example, by John Arquilla in Foreign Policy recently) have not been persuasive. True, there has been a resurgence since 2004 of what statisticians (if not humanists) would call "minor armed conflicts.” But, in the case of "high-intensity” conflicts or wars (defined as entailing 1,000 or more battle deaths in a year), the trend-line has been sloping unequivocally downward. And that goes for war-related civilian deaths as well.Explanations of this phenomenon vary. In the case of the post-Cold War New Peace, the best is simply the huge upsurge in conflict prevention, conflict management, negotiated peacemaking, and post-conflict peace-building activity that has occurred over the last decade and a half – most of it spearheaded by the much-maligned UN.For the Long Peace, the most intriguing explanation – and, I think, the most persuasive, though many may disagree – is that since the end of World War II, a fundamental normative shift has occurred among the major powers’ policymakers. Having witnessed the ravages of the last century, they simply no longer see any virtue, nobility, or utility in waging war, and certainly not aggressive nuclear war. That doesn’t mean that we cannot stumble into a war – or a nuclear exchange – through accident, miscalculation, system error, or sabotage; but, it hugely reduces the risk.The greatest test for this thesis in the years ahead will be how China and the United States react to the dramatic shift now occurring in their relative economic, and eventually military, power. President Barack Obama’s re-election offers reasonable hope that the US will give some strategic space to China through a policy of mutually accommodating cooperation, rather than insisting on dominance or primacy. But how will China behave under its new leadership?In a deeply thoughtful recent speech at the Brookings Institution in Washington, DC, Kevin Rudd, Australia’s Mandarin-speaking former prime minister, described possible external scenarios for China over the next decade. They ranged from actively pursuing zero-sum power politics aimed at dominating the hemisphere and beyond, to engaging strategically with the US and other partners in Asia to sustain and enhance the existing rules-based international order. While suggesting that it would be prudent for countries to hedge against the worst-case scenario, Rudd made clear that he is an optimist: provided the rest of the world maintains a policy of cooperative engagement with China, incoming President Xi Jinping and his team will choose a non-confrontational path.Optimism is a good call in this context, and also more generally. There are strong historical grounds for believing that waging aggressive war has simply run its course as an instrument of state policy. Having exhausted most of the alternatives over the years, national leaders have begun to internalize the virtues of cooperation.Moreover, in foreign policy, as in life itself, outlooks can be self-reinforcing, and self-fulfilling. Pessimists see conflict of one kind or another as more or less inevitable, and adopt a highly wary and competitive approach to the conduct of international relations. For optimists, what matters is believing in and nurturing the instinct of cooperation in the hope, and expectation, that decent human values will ultimately prevail. If we want to change the world for the better, we must start by believing that it is possible.THE author is a  Australia’s foreign minister for eight years and is currently Chancellor of the Australian National UniversityProject Syndicate