There are few paradigms more tightly connected with the Scottish Enlightenment than the four stages theory. Yet it arguably remains one of the least understood.
In the second half of the eighteenth century, a whole host of famous Scottish thinkers – Adam Smith, Adam Ferguson, William Robertson, Henry Home (Lord Kames) and John Millar – attempted to explain a range of social phenomena according to a single, universal narrative of the history of progress. The spirit of the paradigm was that the fundamental distinguishing components of societies lay not in accidents of climate, religion or race, but rather in the social, psychological, legal and cultural effects of the history of property and sustenance relations. While French thinkers such as Anne Robert Jacques Turgot used three stages to achieve similar analyses, the Scots preferred four:
- Hunting, where property only extended to what one could carry on one person (savagery),
- Pastoralism, where shepherding witnessed the development of animal property (barbarism),
- Agriculture, where society became settled and landed property became pivotal in the production of sustenance (civilisation),
- Commercial society, defined by contemporary Europe.
The paradigm has, for good reason, been widely identified as a pioneering step in the development of various disciplines of the modern social sciences. At the same time, in taking the commercial society of eighteenth-century Britain as the pinnacle of the history of liberty, postcolonial scholars have, with validity, critiqued it as a blatant example of Eurocentric world historical narration.
John Millar, the protégé of Adam Smith and Regius professor of civil law at the University of Glasgow for nearly four decades at the end of the eighteenth century, is often cited as the most systematic articulator of the four stages theory. Attention has been paid particularly to his reflections on the history of family and gender, which constitute the great bulk of his stadial theory-infused magnus opus, the Origin of the Distinction of Ranks.
I began research for my book John Millar and the Scottish Enlightenment: family life and world history with the intention of revealing how Millar managed his oft-celebrated cohesion. In fact, I was quickly confronted with lacunae, gaps and contradictions with Millar’s stadial analysis. Digging deeper, I realised that these arose from his difficulties in overcoming a complex intellectual web of competing analytical frameworks using evidence and existing scholarship that defied any easy organisation. Moreover, it became clear that his intention was much less to innovate any coherent science of stage-based analysis than to set out his convictions about politics, the family and the nature of authority.
Too often, Millar’s lack of full coherence in his use of stadial analysis has been attributed to intellectual underperformance. In my book, I take a different approach, viewing Millar as a guide to the history of knowledge underpinning the pursuit of stadial history, with a particular focus on gender and the family. Millar used the stadial model as only one of several intersecting paradigms. His deployment and innovation of classic natural law structures, such as the history of household authority relations and the tripartite division of marriage struggle, reveals the importance of his professional setting as a professor of law in Glasgow. Additionally, in his retention of religion as a critical means for explaining differences in marriage practices, we see that even Millar had doubts about stadial analysis as a fully convincing alternative to paradigms such as sacred history.
The deeper we probe into Miller’s complex work, the more we discover his Enlightenment spirit of speculative curiosity. His legacy to modern disciplines of sociology and anthropology  lies not so much in the rigidity of his conviction in any single analytical framework, but rather his thirst for cross-cultural comparison and analysis. His extended discussion of topics ranging from matriarchal familial forms and the Amazon legend to national character and polygamy was not intended to tie up loose threads in stadial analysis, but rather to be an ambitious attempt at historicising all dimensions of authority.
– Nicholas B. Miller, University of Lisbon
 William Lehmann, John Millar of Glasgow 1735-1801: his life and thought and his contributions to sociological analysis (Cambridge, 1960).