The critic and journalist Christopher Hitchens left behind a mystery when he died in 2011. A fierce opponent of theism, Hitchens had written a book in 2006—God is Not Great: How Religion Poisons Everything—that not only dissected theism with rational precision but also heaped scorn and ridicule on religious believers. He called his position “anti-theism,” the idea that, not only does God not exist but that his non-existence is a good thing, given the wickedness and delusion enabled over the ages by the very idea of him.

When Hitchens went on tour to boost God Is Not Great, he asked his promoters to find adversaries to debate him wherever he went. The result was a series of intellectual street brawls. In melodious Oxford English and with formidable recall of centuries’s worth of texts, sacred, historical and literary, Hitchens repeatedly mauled his opponents, with charm and erudition. And he spared no contempt for onlookers. “Ha, what a stupid question,” he burst out to a fellow atheist who thought he was being clever by asking Hitchens what right he had to deprive believers of the comforts of their faith.

After the book tour, Hitchens joined panels of fellow “new atheists” to debate believers on a series of related issues—whether the Catholic Church was a force for good, whether religion improved public policy, whether Islam was a religion of peace, and so forth. Hitchens more or less gave the last five years of his life to the cause. Through it all he exuded a deep, righteous wrath for religious hypocrisy and fatuousness.

And so it comes as a shock to anyone who follows Hitchens to discover that the founder and firebrand of anti-theism admitted he would not, given the opportunity, rid the world of religion altogether. In a symposium with his fellow “horsemen” and again in a conversation with his debating opponent, pastor Douglas Wilson, Hitchens says if, mirabile dictu, he had managed to turn the masses away from religion one mind at a time, and he came before the last believer, he would not be able to deliver the coup de grace. He would not drive religion from the world. This admission is extraordinary in itself: Hitchens seemed to lack the courage of his convictions, something he made a point of never lacking.

Then comes an even deeper shock: Hitchens appears not even to know his own convictions. Asked why he would not extinguish faith, he admitted, twice, that he did not know. Although he proffers some desultory Hegelian thoughts about needing an antithesis to sharpen his thesis and liking the sport of debate, what stands out is his lingering “I don’t know.” He remained haunted by the question’s unanswerability, he said in 2009.

If I may be so bold: I can answer Hitchens’ question for him. I know why he would not kill religion.

The answer can be recovered from the things Hitchens wrote and said about free speech. If this essay were simply an exercise in Hitchenology, a matter of resolving a tantalizing biographic conundrum about the man, I wouldn’t bother, partially because I couldn’t imagine Hitchens being interested in such efforts himself. Stick to the issues, I hear him saying.

Well, the issue, free speech is an all-important one, and Hithens is a radical defender of it. The only thing Hitchens requires of a proposition for it to be worthy of defense is for it to be sincerely held. It need not be supported by evidence the majority finds credible. Steadfast belief is enough to earn Hitchens‘ respect for the sanctity of the individual mind, no matter how out of step it seems with the received view or the authority of experts.

This much we can learn from Hitchens’ defense of historian David Irving’s right to deny the Holocaust. Despite the wealth of evidence indicating the Holocaust happened, Irving retains the right, in Hitchens’ assessment, to conduct research that tries to debunk the standard view, and he has the right to publish books relating his findings. If we forbid such speech, we open the door for governments to prosecute thought crime.

It is well worth recalling that many key scientific discoveries and principles of modern philosophy were once considered so deplorably misguided as to call down the death penalty on their authors. If we wish to keep such power to dictate thought out of the hands of governments, Hitchens believes, we must abide the expression of any sincere opinion, “obviously” wrong as it may be.

Clearly Hitchens has no symathy for Irving’s view, just his right to hold it. Hitchens may have acquired the tactic of seeking out one’s bitterest enemies to vivify one’s appreciation of free speech from Rosa Luxemberg, a life-long heroine of his. “Freedom of speech,” Luxemberg wrote, “is always for the one who thinks differently.” At an international socialist conference in Fance once, Luxemberg’s debate opponent could find no translater to relate his thoughts in French. Rather than let him go unheard, Luxemberg volunteered to act as his translater herself, and she did the job with gusto.

But isn’t Luxemberg wrong in her pithy formulation of the matter? Freedom of speech is for everyone, not just the one who thinks differently. What Luxemburg means to say, I believe, is that the holders of the majority opinion exercise their freedom of speech frictionlessly and with no anxiety of losing it. In this sense, anyone defending a majority view is not even conscious of the constant need for protecting speech freedom. They know they will be heard without taking extra pains.

Consensus provides its own guarantees of freedom of speech. The dissenter lacks this automatic validation.

It is precisely when one is being shouted down by the mob, taken away in handcuffs by the authorities, or subjected to priestly torture that one so keenly perceives the need for protecting free speech. If the man comfortably lodged in the friendly crowd of consensus cannot imagine this perspective, he does not really know what the commodity is he enjoys so fluently and  naturally. This is Luxemberg’s point.

And so Luxemberg’s conception of free speech presents a clear and distinct test of good conscience: one must always be able to imagine oneself in the position of one’s diametrical opponent, and one must respect his right to hold beliefs contrary to one’s own even if one cannot understand his grounds for holding them. Real democratic debate depends crucially on this faculty.

The scenario that Hitchens’ fellow horsemen propose to him, in which he could, by a final act of suasion, rid the world of religion, would be, I believe, too like the scene in 1984′s Room 101 for Hitchens to follow through with it. He could not bring himself to break the final dissenter.  As vile a poison as Hitchens thinks theism is, dissent—in any form–is too precious to be deliberately annihilated, even for a good ideological cause. He will not play-act even a liberal, rational version of O’Brien in Room 101. If free speech is for anyone, it is for Winston Smith, the one who thinks differently.

So why does this curious fact about Hitchens matter to the rest of us? Because it applies to any dispute about ideas, ethics, or politics, and, Lord knows, there are plenty of those these days.

The whole point of reading philosophy and literature is to expand one’s moral imagination, to be able to say to an an ever-larger group of people, “I’m with you.” Luxemberg’s maxim that free speech is for the dissenter reminds us of the best way to broaden our moral imagination. The older we grow, the more we read and think, the more skilled we ought to be at imagining ourselves in the position of our opponents–the more we ought to practice this as a mental exercise.

Who is freedom of speech for? It is for those who think differently from you.