In its worst form, this kind of critique can be self-indulgent, overly academic, and boring. It’s a micro-polemic: a big, philosophical attack on a topic that’s fairly narrow and small. Wuthnow’s critique, though, is ultimately concerned with how people derive knowledge about themselves, which is important. It speaks to the most basic project of public life: people collectively trying to figure themselves out, trading observations about the nature of existence as they all march steadily toward death.

Polls about religion impose neatness on this messy struggle with existence. They rely on tidy categories, marking points to help people see how others are like or unlike themselves. So if, as Wuthnow says, even the best polls are not that good, and they don’t tell us much, it’s worth considering: What fictions about belief get propagated when statistics are used for self-understanding?

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For all its prominence today, modern American religion polling actually has a fairly short history. Wuthnow begins his narrative near the turn of the 20th century, when, “as near as anyone could tell,” he writes, “religion’s influence was declining.” For decades, the U.S. Census Bureau had been tracking data about religious groups; major denominations also tracked their membership and participation. But as the surge of church planting on the American frontier drew to a close, immigrants flooded the country, and religious communities across the country saw declining attendance, clergy faced a new challenge: getting people back into church. To figure this out, sociologists started conducting neighborhood surveys, sending volunteers from house to house with questionnaires. These investigations were also sometimes part of larger attempts to understand urban communities. W.E.B. Du Bois, for example, included interviews with clergy in a massive 1899 study about communal life in Philadelphia.

Looking back at some of these early surveys, it’s remarkable to see how all that’s old becomes new again. In 1926, a Presbyterian preacher named Charles Stelzle convinced 200 daily newspapers to print a questionnaire about religion, God, morality, and prayer; roughly 125,000 readers responded. This method of data-gathering wouldn't pass muster under modern standards—the respondents were likely not representative of the American population, and it would have been impossible to know who the questionnaire missed. But the results still uncannily echo modern times: Nearly a century ago, 91 percent of these poll respondents said they believe in God, compared to the 92 percent who said the same in a Pew poll just a few years ago.

One of today’s polling giants, Gallup, started asking survey questions about religion in 1939. (Again, slightly spooky results: In one poll, 37 percent of respondents said they “happened to go to church last Sunday,” which was the same percentage of self-reported weekly church attenders in a 2013 Pew poll. The methodological differences are crucial, but the irony is still crisp.) Gallup’s engagement with religion polling was critical to its spread, Wuthnow argues, and the organization introduced a novel way of talking about faith. “Polls regularly asked people their opinion of religion,” Wuthnow writes. “They were asked if religion as a whole was increasing or losing its influence on American life. The question assumed they would somehow know, and that the results would somehow be meaningful.”