It is a commonly held belief that democracy can only take root in fertile soil. Countries vary in their historical origins. Some countries were more or less always free, whereas others gained independence from colonial rule only recently. Since the characteristics of the colonizing countries also vary, not even former colonies are all alike. Some countries share a Christian legacy, whereas others have inherited Islamic, Buddhist or Hindu traditions. In some countries people share the same language and ethnic background, whereas in others they are composed of a multitude of such groups. And depending on the historical circumstances under which the state was formed, some countries are big whereas others are small.

Did these historically inherited circumstances affect the prospects for democratization during the third wave? In this chapter, I first review the extant literature on historical factors, here termed domestic social determinants. I then consult the data to test which legacies did have an impact on my full sample of 165 countries in 1972–2006. It turns out that in the main two historical legacies mattered: the share of Muslims in the population, and geographical country size. While still relying on the large-n data, in the final two sections of the chapter I investigate the mechanisms through which these two effects occurred.