PSYCHOLOGY:The evolutionary psychologist Steven Pinker believes we are not just safer in our modern environment but also, crucially, nicer

The Better Angels of Our Nature: The Decline of Violence in History and Its Causes,By Stephen Pinker, Allen Lane, 802pp, €30

AS OUR RECESSION bites and the pain spreads and the anger mounts at those who inflicted the suffering, this may not be the best time to offer 800 pages of optimism about the human condition. Pick up a paper, open a book, watch the news on television . . . the prognosis is dire. Good news is for suckers and evangelicals and ad agencies. We might turn a corner, glimpse a few green shoots, even get a nod from Angela Merkel. But reality will out; the ghouls will be back with the next bulletin. This is not a good time for good news.

We don’t have to look far beyond the internet or dig too deep into the past to see levels of cruelty, both global and domestic, that seem to give the lie to those who advance the cause of progress, such as Steven Pinker, the eminent evolutionary psychologist and author of this book. Torture has always been an acceptable instrument of rough justice and deterrence, not to speak of entertainment. Romans enjoyed terrorising Christians; Christians found solace in doing the same for heretics. We saw al-Qaeda aficionados take a domestic saw to the neck of their victim and gloat as the head came off on YouTube.

Unlike our medieval ancestors we recoil at the public display of sadism. But the practice and the enjoyment continue into the present, only now sanitised by state lawyers to hide the cruelties of rendition, waterboarding and sexual humiliation under a fog of legal redefinition. For some at Abu Ghraib the torture was theatre.

Yet things are getting better. If we succumb to the cynicism that nothing has changed, that human nature is irremediable, then we are simply wrong, according to Pinker. “We are missing what may be the most important thing that has ever happened in human history.”

With that modest claim the author opens his case for the bright side of life. Pinker is a Pangloss, not a Nietzsche; Eric Idle, not Malcolm Muggeridge. The world is a better place than it used to be. If we could imagine a frivolous deity willing to pop us down into any historical era of our choosing, we would be well advised to stay clear of the past and to settle for the present, recession and all.

This should be of some comfort. Despite the savagery of the past century, we have much to be proud of if Pinker is right. Thanks to the Enlightenment, things are getting better, not just in the quantity of violence perpetrated by states and individuals but in the quality of moral sensibilities that guide human behaviour. We are not just safer in our modern environment; we are nicer.

This is a bold enough claim to make of any particular community or period. In the early 1960s, maybe; in Sweden, perhaps, always top of the class in the moral stakes. But it is an audacious assertion about the course of human history. The scope of Pinker’s study extends from prehistory to the present, and the focus is not just on war but on all manner of violence and torture: on cruelty to animals, on the abuse of children, on violence against women. The strength of his argument lies in the claim that in all these areas the evidence is that violence has declined. If he is right, something big has happened, not just to war but to us.

Pinker has a history of challenging received views and puncturing everyday myths. His best-known publication, The Blank Slate, argued against the politically correct idea that we come into the world as blank slates open to cultural manipulation and social engineering. Not so, he said. We are born with the "inner demons" as well as the "better angels" of human nature. Whether that results in more violent or more pacific behaviour depends on how material and cultural developments offer better rewards for co-operative rather than violent behaviour.

Such cultural changes include what the German sociologist Norbert Elias called “the civilising process”: a complex array of social practices and etiquette that helped to redefine the common space of social intercourse and to encourage the inhibition of violence through the invention of good manners.

It became the norm to attend to one’s neighbour at table, not to spit or evacuate one’s nose on the tablecloth, to refrain from copulating or defecating in public. We have forgotten how natural this behaviour once seemed and how intimately connected with pacific relations between individuals and groups such seemingly trivial points of etiquette really are.

It is the emergence of such favourable circumstances, beginning with the Enlightenment and escalating dramatically after the second World War, that Pinker identifies as the key change in global conditions that resulted in the decline of violence. Pinker is well aware that his thesis runs counter to popular intuition, and he devotes half the book to setting out the empirical evidence in support.

A fascinating comparative table of wars and atrocities during the past two millennia questions our pessimistic assumptions about the 20th century. There were 55 million deaths in the second World War, more than in any other single event in history. But that must be seen in proportion to the global population at the time. In the 13th century, 40 million were killed in the Mongol conquests.

To make meaningful comparison with the mid 20th century we must scale by population size. The comparable figure for the Mongol atrocity then becomes 278 million. And that wasn’t the worst. The all-time record is held by the eighth century An Lushan revolt, in China, which most of us have never heard of. Thirty-six million were slaughtered – a sixth of the world’s population at the time. Scaled up for comparison with the second World War, that brings the Chinese death total to a staggering 429 million.

Why do we hold to our pessimism and dismiss the idea of moral progress as an illusion? It may be because more extensive media reporting of contemporary violence since the 1950s tends to distort our perspective. It may be that a belief in the decline of moral standards attracts more donors to our cause. (There is a message here for peace activists.) Or perhaps the relentless scrutiny of contemporary standards in public life tends to bias our judgment in favour of an age when life was gentler and trust was true.

At the end of this extraordinary book, full of passion and wit and surely the most fluent writing in the field of popular science, Pinker leaves us in no doubt about the case for looking on the bright side. “For all the tribulations in our lives,” he writes, “the decline of violence is an accomplishment we can savour, and an impetus to cherish the forces of civilisation and enlightenment that made it possible.”

Bill McSweeney is research fellow in international peace studies in the school of ecumenics at Trinity College Dublin