I started a discussion last week of the “America in decline” thesis by examining an article by the German analyst Josef Joffe published by the US journal Foreign Affairs in its September/October 2009 issue. Joffe tries to refute this thesis, and he has some interesting things to say about it. He points out, for instance, that America is in a different league from other countries and comes out on top on almost every relevant measure of a great power. He reminds us that the US is the youngest country among the world's top players. Its military and its universities are among its main strengths, and they will remain unchallenged for a long time to come, he says. He also says the US has a “unique warrior culture”, which might seem to be a sophisticated version of the conventional idea that the “US is from Mars and Europe is from Venus”. He does not really elaborate on this idea, however, being content instead to say that the US military is a matter of national pride and a ladder for social advancement. The Americans have the “right mindset”, he says, apparently meaning that they consider themselves to be global players who are able to act quickly and decisively. On this count he is probably right: neither the countries of the European Union, with the exceptions of Britain and France, nor China really consider themselves to be global players in quite the same way. More controversially, Joffe adds that the US is the only great nation that knows how to pursue its own interests by also serving those of others. China and Russia are much more egoistical, he says. This might mean two different things, both of them questionable, however. First, it could mean that no country has ever been as generous as the US, though this notion in itself raises many questions. The Egypt of former president Gamal Abdel-Nasser felt that the former Soviet Union was more generous than America, for instance. It is true that no other country has ever put forward a Marshall Plan to help others in their reconstruction after World War II, but this was rather the exception than the rule. Second, it might mean that the US is the main advocate of the “right” political and economic model, representative democracy combined with capitalism, and of the “right” world order. I am sure that many would disagree with this idea for very good reasons, but a serious discussion of it would take us too far from the matter in hand. Joffe also discusses China's economic model of development, which relies on exports and is characterised by weak domestic consumption. He says that this model is not viable in the long run and that something will have to change. Moreover, China is confronting a huge demographic challenge in that it will grow old before it grows rich. China's aging population will require, Joffe writes, a shift from investment to welfare. The issue of America's decline and China's rise was also discussed by the brilliant neo-conservative thinker Robert Kagan and the celebrated British journalist Gideon Rachman in a 2012 debate published on Foreign Policy's website. They emphasised key points that showed that you cannot make predictions if you do not first know history. For instance, while it is true that China might be crisis-prone or exposed to serious internal feuds, this should not lead us to say, as some “experts” have done, that it will not rise to the top. After all, a devastating civil war did not prevent the US from becoming the strongest world power 50 or 60 years later despite the serious economic problems at the end of the 19th century that slowed its rise. Moreover, who can seriously claim that the US will never be exposed to a serious crisis? The last major one was in 2008. A crisis can kill you, or it can strengthen you. I would add that the outcome of a crisis cannot be foreseen, as a lot depends on a country's leadership and the ability of its population to endure hardship and to act collectively. Another interesting question concerns America's allies, which are not in good shape. It is not certain that Europe is able or willing to take care of itself, and this is unlikely to change. It is not certain either whether the US should leave Europe to confront its destiny or try to help it out. It should be noted, says Rachman, that many rising countries (Brazil, for instance) prefer a partnership with China to one with the US. To this Kagan replies by emphasising the fact that China has antagonised many of its neighbours, which now prefer alliances with the US. Things are not so clear cut, he says. There is also the case of countries confronted with an alternative: their economic interests dictate a choice of allies, while their strategic ones impose the contrary. Nobody can say for certain how such countries are likely to behave, but their choices could be crucial. Kagan also reminds his readers that being the world's biggest economy does not in itself guarantee a leadership seat and that power is a much more mysterious thing. The same thing goes for being rich: neither Luxembourg nor Qatar, though very rich, is a superpower. For centuries China was the world's biggest economy, but it was not, far from it, its greatest political power. Geopolitics, alliances, armies, scientific prowess and per capita income all play a role. Geography, for instance, is a blessing for America, as unlike China it is not surrounded by hostile countries. The key word, to my mind, is “influence”, and this needs more subtle definition. Kagan and Rachman disagree on the impact of persistent poverty on the rank and power of a particular country. People tend to forget that China badly lags behind regarding human development, though they both agree that even if China were somehow to manage to become the number one power in the world, it would be a very strange superpower because of its very many poor people. They do not discuss the impact of such huge levels of poverty on China's behaviour, which could turn out to be peaceful or bellicose. The rise of xenophobic nationalism in China points in one direction, while its aging population points in another. China will have to seek resources to support its population, and it could do this peacefully or aggressively. It could be tempted by “great deeds” or adventurism in a bid to support its national cohesion. Last but not least, China, at least for now, does not have, in Joffe's words, the “right mindset”. For the time being, it only wants to dominate the Asia-Pacific region, and it is not sure it wants to be a global player. But it is learning quickly, and this too could change. The writer is a professor of international relations at the Collège de France and a visiting professor at Cairo University.