Power is the cornerstone of international relations. It’s a very well known and currently used concept, but however it’s not so clear, and that’s a problem that we can probably explain why the international system nowadays is not working well it’s because the concept of power is getting ambiguous. In the traditional vision, it seems to be simple, it seems to be obvious, that’s to say power is enforcing ones will to all the other actors by any means, including using violence and including using means, instruments, ways, which are not legal in the domestic affairs. So power seems to be the real sphere of international relations, this free fight among the gladiators as they were called by Thomas Hobbes. Power is the expression of sovereignty, but it’s also the expression of the pure rivalry among all the nation states, which are supposed to be the only actors, the unique actors of the international relations. And so power, in this traditional vision, is pointing the capacity of acting, the capacity of impeding, the capacity of influencing which could be attributed to every nation state, that’s to say every unit in a free fight inside the international arena. It’s really, as it was pointed by so many writers and so many thinkers, it is a world of anarchy, and in a world of anarchy, every unit is able to exist through its own power. In this vision, stability, at the international level, is only possible if we can reach a minimal level of balancing, that’s to say of balance of power. What was true inside the domestic affairs is getting more obvious inside the international arena. That’s to say the only way for keeping peace is to reach a situation of balancing powers in which every power is containing the others and so is preventing the risk of a conflagration, a risk of a total and global war. Otherwise, we are in a situation of permanent war as it was clearly described by Hobbes. Nothing really new from the Leviathan of Thomas Hobbes. This was the vision taken by Clausewitz when he wrote his very famous book <i>On war</i>. But it’s also true about so many political actors and princes during the 19th century and this is for instance the background of the famous bismarckian strategy, this is also the background of the realist theory as it is now well known. But can we be satisfied by such a vision? In a first approach, all these points seem to be really obvious, seem to be absolutely true, but, if we revise this vision and if we take into account the global transformation of the world, it’s not so evident that it appears. First problem: power is a concept made for defining an individual capacity, does it fit to collective actors like states? What does it mean when people say the power of a state? But my question would be: the power of whom? Is it the power of the president? Is it the power of the government? Is it the power of the administration? Is it the power of the state department in US? Or the Pentagon? Or the CIA? Or the power of the society? Of the economic actors who are playing an important role inside the domestic affairs of these actors? What do we mean? When we say the French power, who is holding the French power? The French president? His prime minister? His government? His administration? The parliament? The parties? The political system? Or the mass media? The main French firms and corporations? The French civil society? There is there an ambiguity to which the realist theory didn’t really pay attention and however, if we want to have a clear vision of how the international arena is working we have to pay attention to the real identity of every unique actor and the power is then changing, that’s to say it is no more this collective capacity, but a fragmented capacity, and from this fragmentation we can sometimes observe that there are oppositions, contrasts and sometimes conflicts. That’s a first problem which has not been really solved by the political analysis. The second problem about the concept of power is that it is a subjective one, not only an objective, which is describing the capacity of an actor, it’s also a subjective, that’s to say I have power if the other recognizes me as holding power. My power is depending on my reputation, on my own reputation, my power is depending on the perception that the others have, and this is probably very ambiguous and it leads to another question, which is so important in our discipline, this is the question of the status of every state. That’s to say, a state has a status, a status of power, which is deliberated, which is decided by all the other actors. If you pretend to have a power but if you are not credible, if all the others consider that you don’t have the power you pretend, you will not be able to act efficiently, and your power will be only a mystification. This subjective dimension of power is also pointing out another problem, which is the problem of the willingness of every state to use the resources of power that it has at his disposal. A state can have strong resources, strong power resources but however doesn’t want to use and to mobilize them, don’t want to pay the cost of using these resources, and so his power will be only an apparent power, not a real power. Other problem: What is power? How to measure power? Is it depending on resources you have at your disposal or is it depending on your capacity? What is the real expression of power? To hold resources or to have the capacity to solve a problem? It’s quite clear that by now US has very very strong power resources, but is US really able to use these resources with success? That’s to say is US really capable? Has US the capacity of solving the problem it is facing? That is another very difficult dimension. If you consider power as a capacity, your results will be different that if you consider power as resources. You can hold resources and not have the capacity to solve the problem, or you can solve the problem but holding very few resources. This is another ambiguity. Now the problem of balance of power which is so important, which is at the core of the international relations studies, is this concept clear? I don’t think so. What does it mean for instance nowadays? During Cold War, balance of power was meaningful that’s to say the balance between the US and the USSR power. That was clear, or rather clear. But now, what does it mean? What does mean this balance of power between US and Al Qaeda? What does mean these balance of power among actors who are so different and who hold very different kinds of resources? Last problem but not the least: the evolution of power. Is power nowadays meaning the same thing than previously? Now, when civil societies, social actors, non state actors, are more and more present inside the international arena is power so clear? The second problem is related to culture. Previously, we were in a world which was monocultural, but now we are in a world in which there is a competition among different cultures, and these different cultures don’t have the same meaning, don’t give the same meaning to the concept of power. So, what to do when there are different visions of power coming from different competing cultures? And so the problem will be to say: what does power mean in the Chinese culture, in the Western culture, in the Muslim culture and so on? And how can we conceive a global arena in which these different visions of cultures are competing? Now the last problem is a problem of resource, that’s to say: how can we define power in a world in which there are so many different and more and more differentiated resources of power? How can we conceive a hierarchy of powers in a world, which is characterized by an increasing differentiation of resources of power?