In Historical Law Tracts and later in Sketches on the History of Man he described human history as having four distinct stages. The first was as a hunter gatherer where people avoided each other out of competition. The second stage he described was a herder of domestic animals which required forming larger societies. No laws were needed at these stages except those given by the head of the family or society.

Agriculture was the third stage requiring greater cooperation and new relationships to allow for trade or employment (or slavery). He argued that 'the intimate union among a multitude of individuals, occasioned by agriculture' required a new set of rights and obligations in society. This requires laws and law enforcers. A fourth stage moves from villages and farms to seaports and market towns requiring yet more laws and complexity but also much to benefit from.

The above studies created the genre of the story of civilisation and defined the fields of anthropology and sociology and therefore the modern study of history for two hundred years. Home was also on the panel of judges in the Joseph Knight case which ruled that there could be no slavery in Scotland. He enjoyed intelligent conversation and cultivated a large number of friends, among them John Home, David Hume and James Boswell.