Stewart’s biography of Smith where he describes the method as ‘Theoretical’ or ‘Conjectural’ or ‘Natural’ History.42 The example that Stewart chooses to illustrate Smith’s use of the method is the ‘Considerations Concerning the First Formations of Languages’. Smith attached this essay to Moral Sentiments from the third edition of 1767 onwards, and it is a good illustration of his more general approach to historical explanation. As Stewart points out, it is impossible for us to gain knowledge of the actual early development of language and yet, to quote him,
if we can shew, from the known principles of human nature, how all its various parts might gradually have arisen, the mind is not only to a certain degree satisfied, but a check is given to that indolent philosophy, which refers to a miracle, whatever appearances, both in the natural and moral worlds, it is unable to explain.43
Theoretical history is a form of scientific explanation that provides a plausible account of the operation of some particular phenomenon by using the known to account for the unknown.
Smith’s theory of language deals with an issue that was discussed by a number of eighteenth-century thinkers in just such a way. In the absence of a direct historical record, he theorizes a situation based on what we know of human behaviour and what we know of the basics of social interaction. Two ‘savages’ meet and very soon develop vocal signals to identify common objects. This aids communication between them and gradually evolves into a system of classification based on the association of ideas. As a result, languages develop through a ‘natural’ disposition to name similar objects in a similar way and then to develop this into a class of objects, and then into a way of describing the plural from the singular occurrence of the same object. So a thing (tree) becomes a word ‘tree’ which becomes a plural ‘trees’. Similarly, the quality that marks out the class develops from a description to a quality, so green becomes greenness. Languages then develop words to describe the relation between objects and to allow us to differentiate between them. From here we see the development of linguistic categories and concepts such as numbers, gradually leading to the development of grammar and an evolved standardization of pronunciation. For Smith, languages develop from everyday use rather than abstract philosophy, and so these concepts exist before we recognize them on the level of philosophy. Languages give us the basis for abstract thought, and this continues to evolve as we develop written languages. The theoretical account of language is one based on its gradual evolution from the unintended consequences of human social life.44
Conjectural history also represents a desire to account for the diversity of forms of human society, and for the fact that societies change form over time. We are faced by a lack of direct evidence of the early history of our own society, so rather than create imaginary states of nature like the contract theorists do, we should instead look to the evidence of the condition of other societies. This method is based on the assumption that there are sufficient underlying universalities of human nature and human social life to make meaningful comparisons. Given what we know about human nature from the observation of human life from the historical record and contemporary societies, we can form theories about the sorts of institutions and practices that may have existed in the distant past. The aim is not to invent history, but rather to create a theoretical understanding of the likely path of human development. What is of interest here is not the history of any one society, but rather to draw on the evidence of different societies to develop a theory of the historical development of ‘society’ as a category of social explanation.
In the Lectures on Jurisprudence, Smith makes extensive use of the method. The lectures include a series of case studies in comparative law where the examples of different legal systems’ responses to shared practices, such as property ownership or inheritance, are used to make generalizations about how similar types of society develop similar practices. Smith draws extensively on Scottish and European examples, but he also draws on the description of the social practices of the Native American tribes that had been provided in the accounts of travellers. This was a way of acquiring information about a society that existed in a stage of development that was similar to that of our own ancestors.
By comparing several of these accounts, we can corroborate the evidence as accurate on a descriptive level, while at the same time identifying the universal aspects shared by that type of society. We can use the historical evidence to compare and ‘experiment’, discounting material that contradicts what we know about human nature and generalizing from what remains. The point is not to discover absolutely similar institutions or beliefs across societies, but rather to note sufficient similarities to generalize about ‘types’.
In Smith’s hands, this becomes what has come to be known as the ‘four stages’ theory. The theory provides a schema for the identification of types of society based on the main way of securing subsistence: hunting, shepherding, agriculture, and commerce.45 We will discuss the details of Smith’s application of the theory in more detail in chapter 5, but for the present discussion a broad outline of the view will allow us to see the methodology that he adopts to flesh out his application of science to social matters. In the Lectures on Jurisprudence, there are a number of applications of the theory, but perhaps the clearest is the discussion of property. Smith’s aim is to examine the origin and development of property as absolutely necessary to the existence of all societies. Each of the stages of society has a different conception of ownership that reflects the circumstances of that society. Hunting societies tend to have an undeveloped and immediate idea of property in what is currently to hand or in the animal that has just been caught. Later the idea of owning livestock over time emerges in a shepherding society, an idea that extends to ownership of land once agriculture has developed, and eventually property is extended to intangible things like money and shares in a commercial society. Understanding the differences between the concept of property in each type of society gives us a better understanding of the nature of property as a social category, while at the same time helping us to understand how the institution of property functions in our own society.
Another practitioner of the method was Smith’s student John Millar. Millar’s Origin of the Distinction of Ranks (1771) is a classic of conjectural history that applies the Smithian ‘four stages’ theory to basic forms of human social relationship, including that between men and women and parents and children. In each case, he shows how the context, the main mode of subsistence, such as hunting, shepherding, agriculture, or commerce, shapes the form that the relationship takes. In Millar’s hands, this becomes one of the first sociological accounts of the development of gender inequality.
It is worth pausing to note a couple of the implications of this methodology. First, it is absolutely dependent on the idea that there is a universal human nature; that despite the wide variety of behaviour we find in different cultures, there is a shared basic model of human psychology. This means that no one form of social life is any more ‘natural’ than any other, and so crude ethnocentric judgements are to be avoided. The point is not that some societies are defective or corrupted according to some crude normative scale, but rather that they need to be understood in their own terms. The commitment to a universal human nature has several further implications for Smith’s thinking. Smith, unlike some of his fellow Scots, is uninterested in ideas of race or polygenesis: all human beings are the same in his view. More generally, the thinkers of the Scottish Enlightenment also had to defend the idea of a universal human nature from the possibility that human behaviour was directly affected by the physical environment. In the Spirit of the Laws, Montesquieu had detailed experiments with heat and cold that purported to show that the climate had a direct effect on human physical responsiveness. This could then be used to explain why different parts of the globe displayed different behaviour. David Hume, in the essay ‘Of National Characters’, systematically destroyed this theory and demonstrated that differences in behaviour between different social groups are due to social factors rather than differences in climate. The differences between the French and the Germans cannot be explained by radically different climates, nor do geographically dispersed people such as the Jews differ radically in the practices they maintain.
Second,
