stresses several continuous, rather than dichotomous, variables, and it makes global ties influential, but not decisive by themselves. It stresses that regional units of various kinds and sizes remain important to the story of global economic history (Pomeranz, 2013). This tension between diverging scales of analysis, between comparison and connection, prompts one of most fundamental debates within the field of World and Global History. How can we understand processes of regional convergence/integration versus divergence/hierarchy in the ‘modern world’ within a global framework? How do we relate tensions of divergence within a context of increased connections? This debate goes to the core of social sciences. Over the past two centuries, social sciences developed a dominant view that the modern world shows a pattern of more or less linear development in which all positive trends over time converge into a more homogenized world (Wallerstein, 2014). By and large, left and right shared the same belief in the inevitability of progress and the linear upward pattern of social processes. This ideology of ultimate, positive convergence of all states and peoples reached an apotheosis in the three decades after the Second World War. At the same time, a number of analysts began to contest this linear model, arguing that the modern world was also one of heterogenization and polarization (Palat, 2014). When analyzing the social world, the linear versus polarizing models of historical development became a debate about whether the various zones or countries would converge to an approximately equal standard of economic, political and cultural structures. A global perspective shows that, despite the many ways in which there has been convergence, there has been simultaneous and strong polarization. Much of this can only be observed if different scales of analysis are interconnected, if regions are not analyzed as self-contained units, and if the global is not seen as an undifferentiated macro process. The need for a global and historical perspective instigated three, interrelated research strategies facilitating multilayered and multifocal frames of analysis. The first compares individual cases in ‘a two way mirror’, equating both sides of the comparison (reciprocal comparative analysis). The second strategy analyzes the interactions and interconnections between societies or systems, and how those patterns of contact shift (network analysis, translocal/transnational analysis). The third takes human systems in which various societies and their mutual contacts are given shape as the central unit of analysis. Examples include economic systems (the current world-system), migration systems, ecological systems (climate, disease), and cultural systems. Human societies are always linked together by several of these systems and act in reaction to these systems (systems analysis).