In textbooks of international relations theory, it is a common assumption that the international system originated during the seventeenth century, with the Peace of Westphalia as the decisive point of its emergence. As I shall argue in the present chapter, this thesis rests on a presentist apprehension of the terms ‘international’ and ‘system’. As a distinction in the manner of knowing entails a difference in the mode of being, the international system as we know it today did not exist in the Classical Age, no more than it did in the Renaissance. In these periods, there is no object of knowledge called the international system. Take Bull's definition of the term system: ’Where states are in regular contact with one another, and where in addition there is interaction between them sufficient to make the behaviour of each a necessary element in the calculations of the other, then we may speak of their forming a system‘.

To be sure, if we extend the range of application of the term international to cover everything that takes place between states, we are entitled to speak of something international in the Classical Age, even if the term itself was never used by classical authors.