version, this differentiation theory restores the full meaning of functional differ-
entiation and offers powerful insights into periodization that Waltz’s emaciated
version cannot.^47 It is not possible, even in principle, therefore, to use Waltz’s theory
tothrow light on the question of historical periodization. His theory can tell us
something about how anarchy is maintained but nothing about historical shifts from
anarchy to hierarchy or bipolarity to multipolarity and vice versa. It cannot think at
all about shifts outside the segmentary/stratificatory framing, like those opened up
by functional differentiation. This is a key reason why neorealism cannot cope with
the Medieval order, which combined elements of stratificatory differentiation
(popes, emperors) and functional differentiation (churches, guilds).
The limitations of neorealism notwithstanding, IR theorists should be able to
make a contribution to the work of world historians, particularly with the task of
identifying meaningful breaks in the course of world history. As Teschke acknow-
ledges, however, ‘periodization is not an innocent exercise’ because it ‘implicates
IR theories with respect to the adequacy of criteria adduced to theorize the
continuity or discontinuity of international orders’.^48 Yet the reality is that IR theory
as yet has offered relatively little to world historians. As we have noted elsewhere,
there is no IR theory that has matched the success of the ambitious theoretical
framework developed by Wallerstein.^49 His theory, operating at the intersection of
political and economic systems, generates two major turning points in world history.
Before 10,000 BCEhe identifies the existence of mini-systems, where the division
of economic labour never extended beyond the boundaries of a common culture.
These systems then gave way to world systems where the division of labour
extended beyond any single culture and for millennia the dominant political form
was the world empire. After 1500 CE, however, world empires gave way to a single
capitalist world economy, at the centre of which interacted a series of states that
were all sufficiently strong that they could withstand any state with imperial
aspirations.^50 Although this framework was still regarded by McNeill in the 1990s
as the ‘leading candidate’ for world historians, he also argued that they were ‘still
fumbling around in search of an adequate conceptualization of human history’.^51
Moreover, with the further passage of time, it increasingly reflects a Eurocentric
flavour.
We are firmly committed to the view that IR theory has the potential to provide
a framework that will promote a coherent and intelligible approach to the task of
writing world history and also that world history provides the most appropriate
setting for developing and testing IR theory. Whatever its failings, our attempt to
bring together mainstream IR theories and world history did generate a framework
which both located international relations within a world historical setting, and
provided a distinctively IR approach to historical periodization which located the
changing nature of units at the centre of deep-seated historical transformation.^52
Although we would now pay more attention to the nineteenth-century trans-
formation centred on industrialization and capitalism, we still broadly accept this
and other theoretical conclusions that we drew. Yet despite our best endeavours,
there is more than a whiff of Eurocentrism about our historical periodization and
300 The paradox of parsimony