To understand the past – and, often, the present – we group people together, attributing the same characteristics to individuals in a group as we do to the group as a whole, especially when it comes to religion.

Éric Rebillard challenges this approach in a new book, co-edited with Jörg Rüpke, titled “Group Identity and Religious Individuality in Late Antiquity.”

During late antiquity, some religious groups evolved into institutions that enforced normative behavior and created rigid boundaries between “us” and “them.” The rise of the Roman Empire, with its dwindling of local political identities, may have spurred an increasing identity with religious groups, says Rebillard, professor of classics and history in the College of Arts and Sciences. Homogeneity within the group was valued; individuality was not.

Because group identity became more obvious and important does not mean that individuality did not have an equally important impact on historical events, contends Rebillard, who disagrees with historians who treat groups as internally homogenous. This alternate approach was presented as a working hypothesis to a group of scholars; their responses, delivered at a conference in 2011, were collected into “Group Identity.”

The first part of “Group Identity” lays out the legal framework relating to individuals and religion, a relationship that changed dramatically with the implementation of an imperial religion in 250 A.D.

The book’s second section examines the complicated relationship between religions and religious individuals, such as how idiosyncrasy can threaten a religion’s survival. The third section addresses the difficulty of finding evidence of individual religiosity in history. As Rebillard notes, even individuals in religious texts may be group constructs and not representative of an actual individual.

The book’s final section addresses the multiple roles that each person assumes – despite the efforts of particular groups to claim their entire identities. In his chapter, which draws on research presented in his 2012 book, “Christians and their Many Identities,” Rebillard considers the age of Augustine, and in what ways, and when, being Christian mattered in people’s everyday experience.

For many Christians, writes Rebillard, Christian identity was “situational.” As an example, Rebillard offers a sermon Augustine preached in Carthage, exhorting the congregation not to participate in banquets held in pagan temples. The congregants felt their Christianity wasn’t relevant in such a situation, since they knew the idols were mere stone statues and it was important not to offend the superior who’d invited them to the banquet. For them, Christianness was not the guiding principle in all contexts; according to Rebillard, other group affiliations were also identified with only intermittently.

Rebillard then explores incidents at the end of the 5th century that have traditionally been explained as religious conflicts between Christians and pagans. But when examined from the perspective of the individual, Rebillard found even when these individuals acted as a group – as a lynch mob, for example – the “groupness” didn’t outlive the moment of mobilization.

“People identify during the event and then lose the identification,” writes Rebillard. “That groupness occurs intermittently does not mean that it needs to be constructed anew each time it occurs, but only that it is not a constant in everyday life.”

Thus, writes Rebillard, shifting the unit of analysis from the group to the individual “invites us to begin rethinking some of the general assumptions we share about the period” – such as the traditional divisions between Christians and pagans, and the variations thereof.

Linda B. Glaser is a staff writer for the College of Arts and Sciences.