Steven Pinker addressed the Institute of Art and Ideas with his thesis outlining a decline in violence over the course of recent centuries. Is this the case and, if so, why?

"Violence has been in decline for long stretches of time, and today we may be living in the most peaceful era in our species' existence. The decline of violence has not been steady, it has not brought rates of violence down to zero, and it is not guaranteed to continue, but I hope to persuade you that it's been a persistent historical development visible on scales from millenia to years, from the waging of wars to the treatment of children and animals." Steven Pinker

It's certainly a substantial claim, and one that has stimulated much debate over the past year. Some have reviewed his book, "The Better Angels of our Nature: Why Violence has Declined", as a supremely important study of human nature. However, John Gray has attacked it as displaying a misplaced faith in an enlightenment teleology.