We can best open this chapter by pulling together some earlier findings. From Chapter 3 we can pick up the idea of the human capacity to progress. Also from that chapter we can pick up the idea that ‘scientific’ history will deal causally with social institutions rather than with singular events like wars and conquests and, accordingly, that it deals with what is ‘natural’ rather than what is ‘most agreeable to fact’. And from Chapter 4 we can pick up the idea that the most important source of social diversity is the various sets of moral causes and that these make their determining effect increasingly as mankind develops.

By and large this has been abstract and it is now time to look at the content of this development. The content of the history-of-mankind-in-society is principally a history of social institutions. To comprehend that history is, for the Scots, to remove ‘wonder’ by discovering connecting principles. A society's institutions, in other words, are not merely contingently connected either at any particular point in time (social statics) or between one period and the next (social dynamics) but reveal a necessary/natural pattern. It is this pattern that makes social history intelligible. As we will see, this intelligibility was achieved most characteristically by dividing the history of social institutions into four stages and, as we shall also see, the key social institution is property.

A: Locke, Empiricism and Primitive Psychology

Before we see how this was done we have to outline a crucial underpinning premise. Once again the way forward is to return initially to a point made earlier. We saw in Chapter 2 how much emphasis the Scots laid upon ‘evidence’. Human sociality was an empirically established fact. This empiricism exploded all ‘closet metaphysics’ by relying upon what actually is the record of human experience. Humans ‘experience’ the world through the medium of their senses. This doctrine was put on the map, so to speak, by John Locke (see Chapter 1).

To Locke all our ideas come either from sensation or reflection, that is, either from ‘sensible objects without’ or from ‘what we feel within ourselves from the inward workings of our own spirits’ (Essay: Bk 1, Ch. 5 [1854: II, 3]). What is important for our current purposes is a feature of Locke's own way of arguing. In the context of language, he developed a genetic or historical argument.