President Obama prepares to speak during the U.N. Climate Change Conference in Paris. (Evan Vucci/Associated Press)

Each week, In Theory takes on a big idea in the news and explores it from a range of perspectives. This week we’re talking about the shifting world order. Need a primer? Catch up here.

Joseph S. Nye Jr. is University Distinguished Service Professor and former dean of Harvard’s Kennedy School of Government, and author of “Is the American Century Over?

As Henry Kissinger has recently written, there has never been a truly global world order. World order itself is a slippery term. Nevertheless, since World War II, the United States has been the most powerful state in the world and produced a partial world order. It has, albeit imperfectly, led in the production of global public goods, such as a balance of military power, international monetary stability and an open system of trade. The U.S. Navy is crucial in policing the laws of the seas, and in the 2008 financial crisis, the crucial lender of last resort was the Federal Reserve.

If you believe that international politics is not yet (nor will ever be) ready for world government, then global public goods such as security and welfare will depend on the actions of the most powerful states. But a new crop of transnational issues will call for cooperation among all — both the powerful and those gaining in strength.

Many scholars point out that the one thing worse than American leadership is no leadership at all. Order does not produce justice, but some degree of order is often a precondition for it. In that sense, George H.W. Bush’s proclamation of a “new world order” in 1991 was really a statement about the continuation of the post-1945 order.

The fact that the world’s richest country after World War II had a liberal economy and system of government had important implications not only for the creation of an open international economic system, but also for the spread of democratic values and human rights. In that sense, despite our flaws and policy mistakes, it mattered that the United States was an open society. American primacy allowed freedom of choice to others and an openness that was not always true of previous forms of hegemony. Had Hitler or Stalin prevailed, today’s world order would look very different.

States that have benefited from this liberal world order may preserve its institutional framework — its institutions, norms and commitments — out of self-interest. But will they do so if they believe that American power is in decline?

The current conventional wisdom, exaggerated by American campaign rhetoric, is that this is the case. Yet although the United States has many problems (and always has), we are not in absolute decline like ancient Rome, which had no productivity growth. Thanks to immigration, we are the only major developed country that will not suffer a demographic decline by midcentury; our dependence on energy imports is diminishing rather than increasing; we are at the forefront of the major technologies (bio, nano, information) that will shape this century; and our universities dominate the world league tables. We have more allies and connections than any other country.

No single country is poised to overtake the United States in overall power. The real challenge we face could be called “the rise of the rest.” Even though the growth in emerging markets is unlikely to create a single challenger that will overtake the United States, the growing power of these countries creates a more complex global landscape. The problem of leadership in such a world is how to get everyone at the table and still have action possible. There are more participants, more goals and more issues.

In addition to many more actors — both state and non-state — the world agenda will also become more complex. Not only do traditional issues of security and the economy remain important, but the number of other transnational issues has increased — and many of these cannot be fixed through traditional “hard power.” For example, military power is of little help on climate change, pandemics or governance of the Internet.

While American leadership will continue to be important, success in solving the new transnational challenges will require the cooperation of others. In this sense, power becomes a positive-sum game. If the liberal world order is to continue, it will not be enough to think in terms of American power over others. One must also think in terms of combining strength to accomplish joint goals.

The United States will remain central to the balance of power, and American leadership will continue to matter in the production of public goods. But the liberal world order of the future will look very different from that of 1991.

Explore these other perspectives:

Ali Wyne: The world is getting better. Why don’t we believe it?

G. John Ikenberry: American leadership may be in crisis, but the world order is not

Kim Ghattas: One person’s world order can be another’s disorder