The number of atheists in the US has been on a steady incline over the years, according to the Pew Research Center. In 2012, 2.4 percent of American adults said they were atheists, which was up from 1.6 percent in 2007. A recent poll conducted by WIN-Gallup noted a similar rise globally. One explanation for this increase, says Ryan Cragun, a sociologist of religion at the University of Tampa, might be the emergence of the New Atheists — a group of 21st-century atheist thinkers publishing popular books that argue against religion.

The New Atheists came to prominence in 2004 with the publication of Sam Harris' The End of Faith, a book that derided faith as "the devil's masterpiece." The book is purportedly an attack on religious fanaticism, but as reviews point out, it ends up being a full-frontal assault on all religious people, even moderate ones. Indeed, while writing a sympathetic review of the book, The Observer noted that Harris "too often allows anger … to color his tone." Nonetheless, the book spent over 30 weeks on the New York Times bestseller list, where it peaked at number four. The market, it seemed, was ripe for screeds against religion. And over the next few years, several New Atheist books, all highly critical of religion, were published to popular acclaim, including Christopher Hitchens' God Is Not Great and Richard Dawkins' The God Delusion.

Of course, popular acclaim is different than critical acclaim, and even more different than scholarly acclaim. Various scholars have pointed out that New Atheist critiques of religion fall short because they've misrepresented faith, caricatured believers, and engaged in the same fundamentalism they were allegedly impugning.

But Dawkins and his fellow New Atheists are just one kind of atheist; not all those who have denied God's existence over the years have done so in such a vituperative manner. Nor have all of them been as "intellectually lazy as Dawkins and his ilk," wrote Michael Robbins at Slate. As Robbins points out, the New Atheists don't seem particularly "bothered to familiarize themselves with the traditions they traduce" — traditions that include such intellectual giants as Machiavelli, Hobbes, Spinoza, Hume, and Nietzsche, the last of whom being arguably one of history's most influential atheists, the one who codified the phrase "God is dead."

new atheists' critiques of religion fail badly because they engage in the same kind of fundamentalism they seek to impugn

When Nietzsche railed against the teachings of Christ, he at least demonstrated a keen understanding of what those teachings were. Compare that with Dawkins, who, in both The God Delusion and a public debate, questioned whether or not Jesus actually existed. (When pressed in the public debate, he eventually ceded, though not without reluctance.) "Imagine," wrote Eagleton in the London Review of Books, "someone holding forth on biology whose only knowledge of the subject is the Book of British Birds and you have a rough idea of what it feels like to read Richard Dawkins on theology."

So how did we get from Nietzsche to Dawkins, from intellectual engagement to sensational dismissal? This is an issue Nick Spencer raises in his new book Atheists: The Origin of the Species. Spencer, a Visiting Research Fellow at the University of London's Faiths and Civil Society Unit, and Research Director of the London-based Theos Think Tank, wanted to shed some new light on the historical context of atheism, and its various trajectories over the years.

I recently caught up with Spencer to talk with him about some of the key ideas in his book, as well as their broader implications for inter-religious dialogue. This interview has been edited for clarity and length.

Brandon Ambrosino: Why has the New Atheism found such success with the public in recent years?

Nick Spencer: I argue in the book that the reason behind the whole New Atheism spasm was the return of religion to the forefront of global public life in very visible, and sometimes grotesque and violent ways around the turn of century. So sociologists, or some at least, were arguing in the late 1960s that the world was on a steady, progressive course of secularization, and that religion — and certainly public and political religion — were on their way, perhaps, to being replaced by political ideologies or some other commitment.

That clearly didn't happen. What happened in its stead was, for example, for the first time in 300 years or so, some people took to the streets of Britain to burn books, in this instance, the novel The Satanic Verses. Around the same time in America, the so-called Religious Right emerged from what had been a relatively dormant period of 50 or so years, and became a political force to be reckoned with. Elsewhere in the world, there was the Iranian Revolution, and then the horrible acts of mass murder committed in the name of — and in some instances, actually motivated by — religion. So all of a sudden, the wells of moral indignation from which atheists might draw were very, very deep. And I think the positive response to New Atheism as a phenomenon was largely a reaction against that sometimes violent political-religious presence.

BA: Modern atheists seem of a very different variety than their forebears. For instance, Richard Dawkins, whom you critique, is very different than, say, Nietzsche. How did we get from one to the other?

NS: You're right: Nietzsche and Richard Dawkins don't have a great deal in common. I guess I'd say, we didn't get from one to another, because there are different strands of atheisms. I talk about atheisms (plural) in the book. At one point, the statement "There is no God" is acceptable as it is in an academic seminar. But if you wanted to deny the existence of God in public — in the late 19th-century Europe, for example — you'd have to say, "There is no god and therefore ... " There'd have to be some implications of your nonbelief. Atheists over the years have differed according to what those implications are. And the result is that atheists, I argue, differ in their "doctrines," if you like, of the nonexistence of God and its implications for human affairs.

how did we get from nietzsche to dawkins?

Now Nietzsche had one particular, very abrasive, and, I think, painfully honest approach to that question which has spawned in the 20th-century certain nihilistic forms of atheism that are more usually associated with continental philosophy. Dawkins does it right within that tradition, and therefore, is a move on from Nietzsche. He occupies a very different atheistic position (arguably several atheistic traditions) and that's why there is clear blue water between Nietzsche's and his. But it wasn't as if the former ever led to the latter. They were all, if you like, different branches of the same tree.

BA: Who are some atheists you find articulate and compelling?

NS: I would say someone like the British philosopher Julian Baggini. He's an atheist, and quite confidently atheistic. He's not, I don't think, in any way agnostic. He engages in dialogue, if you like. He doesn't assume religious people are stupid, let alone blind. He criticizes their arguments, but not necessarily them. I suppose one might say, if forced to choose one of the New Atheists, Daniel Dennet. There's a British philosopher called Stephen Law — he's a solid philosopher. And then, in a slightly different field, you have someone like the late Ronald Dworkin, a legal philosopher, who was atheist. But again, he's very thoughtful and critical of religion, but one who understands what a sense of the sacred, a sense of religious value actually means.

BA: You're not an atheist; you're a Christian. Do you think that has influenced how you've interpreted the history of atheism?

NS: I'm sure it does. Nobody comes from nowhere. Everyone approaches any subject — whether it's history, or ethics, or philosophy — from a particular vantage point. I don't doubt that my own Christian faith probably somehow, if only subconsciously, influenced how I engaged with this issue. That said, I did my utmost to be as impartial, objective, and fair-minded as I could be in the book. And I have been gratified that a number of reviews have commented on the fact that my book is a sympathetic, fair-minded account rather than a partial, polemical one. So, sure I have been influenced by where I come from, but I don't think unduly.

BA: Your book starts out with claiming the science/religion dichotomy is a modern myth. When did that myth originate and why?

NS: That particular myth of science versus religion originated in the last third of the 19th-century and it was partly, but only partly, a response to Darwinism, and some of the ecclesiastical responses to Darwinism. But it was more to do with the political assertion of the papacy in the last few decades of the 19th-century, and the sense that the papacy was setting its faith against progress, science, and liberalism. It was in the shadow of that concern that the idea first developed that religion and Christianity had always been opposed to science.

"The impetus for the scientific revolution was explicitly christian"

Historically speaking, that's nonsense. If you go back to the 17th-century, you'll find that the impetus for the Scientific Revolution was very heavily, sometimes very explicitly, biblical and Christian. But nonetheless, that particular myth of science versus religion picked up steam in the late 19th-century and is now taken as received wisdom.

BA: So you think the rise of atheism was motivated more by political than philosophical reasons?

NS: I wouldn't necessarily say it was more political than philosophical. I hope I'm clear in the book about this: nonbelievers and atheists don't believe in God just as Christians or monotheists do believe in God. I'd never say one's political or social motivations were the real drivers. I think there are clearly philosophical or perhaps scientific issues there.

The point of the book is, if you like, human beings are more than simply brains or bundles of cognitive reactions. And the culture in which atheism developed in Europe was very thoroughly, deeply, thickly Christian. So what that meant was, from an earlier stage, atheism was as much political — or, I should say, as much a cluster of political and social positions rather than a narrowly intellectual one. And that's the same today. It's not that atheism is more political, or that it's really political. It's just that it's also political. And importantly political, too.

BA: There's been a push over the last few years to deny that religious belief has ever resulted in anything positive for society. Could you give an example of religion benefiting culture?

NS: I'll give you a few examples. First is the concept of what the human is, and in particular, human dignity. The virtue of humility, for example, was a totally foreign one to the ancient world. And the idea that slaves might be possessed of exactly the same kind of dignity and worth as free men was also pretty anomalous — not unheard of, but pretty anomalous. And those were ineradicable commitments of the early Christian community that led to, for example, the challenging of the games in the arenas, and the challenging of ancient exposure of infants (what we would call infanticide). There were some very critical things said of the attitude of the rich to the poor in ancient world, and very critical things said — at least pre-Constantine — to the nature of war and conflict and violence.

"human beings are more than simply brains or bundles of cognitive reactions"

That all changed the way we thought about humans, the way Europe thought about human value and worth, in a way that had enormous implications. It had a rough ride during the late antique period as the Roman Empire collapsed, but ultimately it had a very profound effect on Europe. If you scroll forward a thousand year or so, what you find in the papal reforms of 12th- and 13th-centuries is mentally a very aggressive, self-possessed papacy. But one that, albeit unintentionally, chastises and begins to limit secular, temporal power. And so what we have is what the historian Larry Siedentop called The Origins of Western Liberalism: the concept of the rule of law, justice for all, limited temporal power, and so forth, that can be traced reasonably and clearly through to Christianity, and ironically, to the papacy.

At the other level, the very concrete impact of the transatlantic slave trade, which was first initiated by Quakers in the 18th-century, was driven home forcefully by Evangelicals. And there are other examples one might give, such as the impacts of thinkers like John Locke on political accountability and toleration. So there have been a variety of benefits.

BA: You argue in Doing God that it's impossible to take God from the public arena. Why is that?

NS: Two reasons, really. One is that the public arena is just that: it's the place where people interact with one another, and decide how society should be run. If you're going for that, then you musn't force hypocrisy on people; you must allow them to come to the table of public debate with their own commitments, presuppositions, and so on. To say, "You can only participate if you do so by leaving your religious commitments at the door, and participate as a secular thinker" is to limit or prevent people from engaging honestly. In terms of basic political justice, I think it's incumbent to allow people to bring their faith commitments to public debate. That doesn't mean it's a "get out of jail free" card, or that just because you are religious, you somehow have priority over the debate. You still need to make case in the bar of public opinion. But you have to make it as a Christian, or as a Muslim, or indeed as an atheist.

The second more practical point is that the world is a very religious place. Just because there are some parts of Western Europe and the US, and some parts of the developed world in which a normative secular approach has been adopted, I don't think that's an effective way of dealing with issues that are themselves thoroughly global now.

BA: How can atheists and believers alike go about "doing God" in public is more productive ways?

the myth of science versus religion originated in the 19th-century and is now received wisdom

NS: Some answers are low-hanging fruit: avoid caricature, name-calling, and abuse, do your utmost to understand where other people are coming from, allow them to speak in a language and according to a logic that is true to their condition, be opposed to demanding that they speak your language. At the same time, make sure they realize their responsibility to engage with you on your terms as much as possible, rather than just steamroller through the debate on their own terms. And recognize that what has been called Modus Vivendi Liberalism — a liberalism that typically tries to allow people to get on as best as possible — is a muddy and difficult and awkward place to be.

We are not necessarily going to agree; we can seek agreement, but when we don't achieve it, it's incumbent on us to try and disagree amicably rather than name call. In one sense, that's the answer to any question of serious public debate — it needn't be specifically religious and atheist.

Atheists: The Origin of the Species was released July 3 from Bloomsbury Academic.