Why are women paid less than men? Why were there riots in some north-western English cities in 2000, but not in London? What is the significance of bloggers or of the World Social Forum?

One of the strange features of our times is that well-educated people can get by with very little idea of how to answer questions like these. Many people rely on very simple interpretive frameworks to make sense of what they see around them or on the evening news. So, for example, conflicts between Muslims and Christians are ascribed to culture or history. Gender pay gaps are interpreted as the result of misogyny. The internet is ascribed with magical powers to turn the tables on multinational corporations or governments.

Anyone involved in social innovation needs better ways of thinking, both to grasp the possibilities and the barriers and to understand why apparently better ideas may not spread and scale.

Charles Tilly's work was probably the outstanding contemporary example of an engaged but theoretically rigorous sociology. It is a symptom of sociology's relative detachment that he remained largely unknown outside academic circles, even though he was one of the most fertile thinkers in US social sciences, combining a rare sharpness and a breadth of interest, covering diverse topics ranging from the rise of the state in 18th-century Europe to racial inequality, and from political violence to the conditions for democracy in central Asia. In some ways he was old fashioned – he offered explanations and showed how some things cause other things to happen. His accounts have real people, history and drama, and have consequences for how change might be achieved more successfully. They are thus very different from the sweeping generalisations, usually detached from any detailed analysis, of some of the most fashionable social theorists.

Like all of the best sociologists, Tilly started with close observation. Pay inequality is a good example, which Tilly investigated along with many other kinds of inequality in his book Durable Inequality. Economists have found it hard to explain why gender pay gaps are so persistent, since in a properly functioning labour market employers should have incentives to reward women as much as men for their skills and their work.