I Modern societies
Modernization originally referred to the contrast and transition between a ‘traditional’ agrarian society and the kind of ‘modern’ society that is based on trade and industry. For example traditional and modern would describe the difference between medieval England and late-Victorian Britain. A traditional society is ‘vertically’ organized by hierarchical division by class or caste — a specialization of prestige. But a modern society is ‘horizontally’ organized by function, such that the major functions are performed by modular social systems. These major social systems include the political system, the public administration (civil service), the armed forces, the legal system, the economy, religion, education, the health service and the mass media. So, while a traditional society is like a pyramid of top-down authority, a modern society is more like a mosaic held together by the cement of mutual inter-dependence. A further contrast is that traditional societies consist of a single, unified system with a single centre of power; while a modern society is composed of a plurality of autonomous systems which interact with each other, influence each other, but do not absorb each other. Modern societies are fundamentally heterogeneous with multiple centres of power; and this is no accident
The Modernization Imperative but intrinsic to their nature. Indeed, the continued process of modernization tends to break down any remaining vestiges of hierarchy and centralized domination of social functions. Modern and traditional societies differ according to their complexity of organization and their rate of growth in complexity. Modern societies are much more complex than traditional societies and are growing ever-more complex. Traditional societies are simpler and have a static structure (or one that increases its complexity so slowly or erratically that they perceive themselves as static). Complexity is favoured by selection processes, which are more powerful in modernizing societies, because specialization of function enables greater efficiency (for instance when division of labour, or increased trade and communications enables greater efficiency). Increasing efficiency then frees resources and drives further growth.1 Modern societies are based upon growth and the expectation of growth. Indeed the cohesion of modernizing societies requires more or less continuous growth. This is why it is impossible to stop modernization at a particular favoured point — if growth stops then the nature of society reverts towards a traditional form. Growth in modern societies includes economic growth (increasing output and productivity), but also entails ‘cognitive growth’ — which means an increase in knowledge and capability across a wide range of activities such as science, technology and political administration. Traditional societies exhibit division of labour and cognitive specialization, but their complexity is constrained by the hierarchical structure into three main categories of peasants, warriors and priests (Gellner’s ‘plough, sword and book’). Warriors and priests constitute the ruling class who are concerned mainly with maintaining social cohesion by means of physical coercion and ideological propaganda. Peasants — whose role is agricultural production — constitute the vast majority of the population of traditional societies. Beyond the division into warriors,  For discussion of the meaning of ‘complexity’ and ‘selection’, see Appendix.
Defining Modernization priests and peasants there is only a small ‘middle class’ of technical specialists (for example the different types of craftsmen). But in modern societies the ‘middle class’ is dominant: the vast majority of the population is cognitively specialized, and there are many thousands of distinctively different occupations. A deeper understanding of modernization reveals that one vital qualitative difference between...