Is progress possible? I took part in a panel discussion of that question some time ago.

The answer is obvious and undeniable, I said. We are by far the wealthiest and healthiest people who ever lived. If the child mortality rate today were the same as it was only a century ago, I said, one in five people in the audience would have died before celebrating their sixth birthday. That's progress.

Of course progress hasn't delivered us to Nirvana, I added. And as we learned in August, 1914, progress can be halted or reversed in the future if we fail to choose wisely. But progress is real. And we should be grateful for it.

The response was something close to a collective shrug. Yes, yes. We're healthier and wealthier, which is nice. But - someone in the audience asked - what about moral progress?

I was taken aback. Having spent a lifetime reading history, I think the case for moral progress is even more obvious. But where to begin? Look at slavery, I finally said. It was close to universal throughout human history. Now it's banned worldwide. That's moral progress.

This was greeted with more shrugs and new objections. "Yes, but ..." That sort of thing. Lots of people really do not want to acknowledge that our species is not entirely wretched or that our current existence is somewhat better than a vale of tears.

This fact is on prominent display right now, thanks to the publication of Steven Pinker's Better Angels of Our Nature: Why Violence Has Declined.

"This book is about what may be the most important thing that has ever happened in human history," it begins. "Believe it or not - and I know most people do not - violence has declined over long stretches of time, and today we may be living in the most peaceable era in our species' existence."

What follows is evidence. Heaps of it. Mountains, in fact. More than half the book consists of research which shows we are far less violent than at any time in history.

I won't even attempt to summarize it here. Suffice it to say it is overwhelming. And fascinating, thanks to Pinker's light and lively writing style.

It is also not new.

That's not a knock at Pinker, a renowned Harvard psychologist. It's just a fact, which he happily acknowledges: Pinker is the first to collect all the data in one book - from political science, anthropology, criminology, and so on - but it's well known among specialists.

And not only them. I wrote about it in my 2008 book Risk. I've also written countless columns about the decline of homicide rates, war, torture, slavery, terrorism, cruelty to animals, and just about every other form of violence.

I always get the same response Pinker is now getting.

Some are startled and want to learn more. A greater number say "yes, but" and rush on to discuss how awful this or that current reality is. Others flatly reject the claim as the self-evidently absurd belief of a ridiculous Pangloss.

Odd, isn't that? It's like a patient angrily telling his doctor he's wrong after he's told he doesn't have cancer. Why won't people at least consider the possibility that their pessimism is misinformed?

Pinker suggests a number of reasons.

One is the fear that acknowledging progress would foster complacency. "Also," Pinker writes, "a large swath of our intellectual culture is loath to admit that there could be anything good about civilization, modernity, and Western society." More basically, the increasing sense that violence is morally wrong means it repulses us, and grabs our notice, far more than it would have in the past, creating the illusion that violence is not declining: Today, a lynching would draw worldwide attention and condemnation; a century ago, people wouldn't have cared enough to shrug, let alone report the incident and discuss it.

Then there's basic psychology.

We form intuitive impressions of how common something is based on our ability to recall an example of that thing. Combine that fact with the news media's love of stories about people doing horrible things to people. And add the fact that there are seven billion people on the planet, which ensures that there are always stories of people doing horrible things to people, not because such acts are common, but because there are so many people.

Result: We have a constant intuitive sense that even the most horrific acts of violence are common. And getting more so.

Finally, there's a very basic reason that Pinker doesn't mention, at least not explicitly. But some reactions to his book illustrate it perfectly.

It's confirmation bias: When we believe something is true, we don't naturally test our belief by dispassionately seeking out and considering the available evidence. Instead, we tend to grab onto anything that supports our belief while avoiding evidence that contradicts it - and if it's thrust under our noses, we rationalize like crazy to make it go away.

Google Steven Pinker's name and his book title and you will find countless comments about his claim that violence has fallen dramatically. Lots say it's nonsense. And most of those are based on the claim alone, not any consideration of Pinker's voluminous evidence. Even the British philosopher and public intellectual John Gray breezily dismissed Pinker's claim in an essay which ignored almost all the "impressive-looking graphs and statistics" - Gray's words - in Pinker's book.

No evidence can possibly convince those who refuse to consider evidence. And far too many people refuse to do the hard work of seriously testing their intuitions, assumptions, and world views against the available evidence.

"To see what is in front of one's nose needs a constant struggle," George Orwell wrote. But blindness is a breeze.