The Atlantic

But, as Armstrong points out in the book, “there is no universal way to define ‘religion,'” particularly when it comes to comparing mono- and polytheistic faiths. “In the West we see ‘religion’ as a coherent system of obligatory beliefs, institutions, and rituals … whose practice is essentially private and hermetically sealed off from all ‘secular’ activities,” she writes. “But words in other languages that we translate as ‘religion’ almost invariably refer to something larger, vaguer, and more encompassing.” This is an important premise of one of Armstrong’s main arguments: It’s impossible make a coherent case about the role of religion in warfare and violence throughout history and across the world, simply because religion plays very different roles in different cultures.

For example, religious belief and practice in, say, ancient Mesopotamia were very different than what they have become in modernity—a period that Armstrong and many academics say began in the West in 1648, when peace treaties ending several major wars in Europe were signed in Westphalia, a region in present-day Germany. She describes the spread of more secular governments in the West and the decline of religion as a primary organizing force in many people’s lives during this period. Although “religious” violence has always had a political element, she argues, the political nature of warfare—even in wars with putatively religious justifications—has become even more pronounced in contemporary history.