“The Four Horsemen: The Conversation That Sparked an Atheist Revolution” is a transcript of a 2007 conversation among four prominent public intellectuals, each the author of a best-selling book challenging the intellectual and moral credentials of religion.

Its participants were the celebrated evolutionary biologist Richard Dawkins (“The God Delusion”), the grandfatherly philosopher Daniel Dennett (“Breaking the Spell”), the brash neuroscientist Sam Harris (“The End of Faith” and “Letter to a Christian Nation”) and the late crusading journalist Christopher Hitchens (“God Is Not Great”). Their conversation was an invigorating example of what happens when astute, inquisitive minds engage together on deep questions.

We’re fortunate that the exchange was captured on film, and the video has since been viewed millions of times online. Why then do we also need the book?

I find that the print volume adds something new to the public record: Not only do the surviving members of the foursome — Mr.  Dawkins, Mr. Dennett and Mr. Harris — but also each weighs in with fresh thoughts on the subjects they discussed, the text affords a different, more reflective way of processing the truly vital exchange of ideas. This slim volume (130 pages) is chock-full of observations that secular readers will find thrilling and believers will find challenging. Those concerned to understand religion as a natural phenomenon will derive special benefit from ruminating over its pages.

As you might expect, the four agree on many things: that religious dogmatism hinders the growth of humanity; that believers wield a double standard to make honest criticism of religion seem out of bounds; that religions need to hold themselves to the same intellectual standards they apply to other religions; that it isn’t fair game to employ argumentative tactics that can be used to rationalize anything.

Mr. Dennett, for example, points out that you can “play the faith card” to excuse things that are “manifestly fraudulent” (to buttress a belief in Earth’s flatness, for example). If there is a principled way to distinguish between permissible and impermissible articles of faith, why haven’t any of the world’s religions provided it? If there isn’t, why don’t we wise up and treat “It’s an article of faith for me” as what it truly is: a defiant and disqualifying breach of rationality norms?

The four deliberate at length on the feedback they get for criticizing religion in such a forthright manner. Are they insensitive to people’s need for comforting beliefs? Perhaps.

Are their convictions just as dogmatic as those they criticize? No, there’s a difference between having an evidence-based conviction and rationalizing a cherished belief. Is a scientist’s reliance on evidence and argument tantamount to a believer’s reliance on faith?

Doesn’t the former, like the latter, involve trusting something? You can certainly point to similarities, but there are also differences: Evidence helps scientists converge on reliable truths, while faith tends to generate divergent and mutually irreconcilable worldviews. The horsemen’s rebuttals are by turns flippant and trenchant, but, time and again, they seek to learn from their critics.

For example, they often credit their detractors with being motivated by understandable concerns, and do what they can to bring the valid considerations to light. The conversation ends up being a kind of master class in how to conduct an honest, searching, growth-oriented conversation.

The four don’t just dwell on points of agreement. Two participants — Mr. Dennett and Mr. Harris — are particularly eager to explore differences. Is all religion toxic or only some? Might some need the community and solace that religion affords? Is there a place in our lives for the sacred? What do people mean when they describe themselves as spiritual or say that they’ve experienced self-transcendence? Should secular thinkers seek to provide alternatives to religious ways of talking about profound experiences? Isn’t it important that we valorize (some) such experiences? Yes, the anti-intellectual tenor of our times seems to be driven by irrational fears, but is it possible that the quest for knowledge has gone too far? Aren’t we better off not knowing certain things? Could the sciences give us more understanding than is good for us?

This bracing exchange of ideas crackles with energy. It’s fascinating to watch four first- class minds explore a rugged intellectual terrain, calling attention to remarkable features of the landscape. The textual transcript affords a different experience, one that, for me at least, is even more rewarding. I commend the book to those seeking an honest reckoning with their religion — and those curious about how the world looks from a rigorously naturalistic and atheistic point of view.

Andy Norman is the Humanism Initiative director at Carnegie Mellon University: anorman@cmu.edu.

First Published: March 16, 2019, 2:00 p.m.