Prosopography is an investigation of the common characteristics of a group of people, whose individual biographies may be largely untraceable. Research subjects are analysed by means of a collective study of their lives, in multiple career-line analysis. The discipline is considered to be one of the auxiliary sciences of history. British historian Lawrence Stone (1919–1999) brought the term to general attention in an explanatory article in 1971, although it had been used as early as 1897 with the publication of the Prosopographia Imperii Romani by German scholars. The word is drawn from the figure of prosopopeia in classical rhetoric, introduced by Quintilian, in which an absent or imagined person is figured forth—the "face created" as the Greek suggests—in words, as if present. Stone noted two uses of prosopography as an historian's tool: first, in uncovering deeper interests and connections beneath the superficial rhetoric of politics, in order to examine the structure of the political machine; and second, in analysing the changing roles in society of particular status groups—holders of offices, members of associations—and assessing social mobility through family origins and social connections of recruits to those offices or memberships. "Invented as a tool of political history," Stone observed, "it is now being increasingly employed by the social historians." Prosopographical research has the goal of learning about patterns of relationships and activities through the study of collective biography; it collects and analyses statistically relevant quantities of biographical data about a well-defined group of individuals. The technique is used for studying many pre-modern societies. The nature of prosopographical research has developed over time. In his 1971 essay, Lawrence Stone discussed an "older" form of prosopography which was principally concerned with well-known social elites, many of whom were already well-known historical figures. Their genealogies were well researched, and social webs and kinship linking could be traced, allowing a prosopography of a "power elite" to emerge.