Over the past two centuries, the dominant view in social science has been that the modern world shows a pattern of linear development in which all positive trends go upward in more or less linear fashion (albeit perhaps at an uncertain speed), and that therefore over time discrepancies between the leaders and the laggards are overcome, toward a relatively homogenized world. This view was shared by classical and neoclassical economics, by what was called Whig historiography, and by most of traditional sociology and anthropology. Classical or orthodox Marxism, while very opposed to a liberal Weltanschauung, shared, by and large, the belief in the inevitability of progress and the linear upward pattern of social processes.
In the post 1945 period, a number of analysts began to contest this linear model. Rather than viewing the modern world as a process of homogenization and therefore of overcoming gaps, many social scientists began to argue that the modern world was one of heterogenization and polarization, indeed a pattern of escalating polarization, which was itself the outcome of the way in which the modern world was structured.
An intellectual collaboration of ten research working groups has been evaluating the empirical evidence in this fundamental debate. The research has been large in scale and long in duration. The object of analysis has been the existing world system as a whole over the whole of its effective existence of the past 500 years and will be covered in a semi-final draft of this collective international research project of social scientists.