MELBOURNE ― With daily headlines focusing on war, terrorism, and the abuses of repressive governments, and religious leaders frequently bemoaning declining standards of public and private behavior, it is easy to get the impression that we are witnessing a moral collapse. But I think that we have grounds to be optimistic about the future.

Thirty years ago, I wrote a book called “The Expanding Circle,” in which I asserted that, historically, the circle of beings to whom we extend moral consideration has widened, first from the tribe to the nation, then to the race or ethnic group, then to all human beings, and, finally, to non-human animals. That, surely, is moral progress.

We might think that evolution leads to the selection of individuals who think only of their own interests, and those of their kin, because genes for such traits would be more likely to spread. But, as I argued then, the development of reason could take us in a different direction.

On the one hand, having a capacity to reason confers an obvious evolutionary advantage, because it makes it possible to solve problems and to plan to avoid dangers, thereby increasing the prospects of survival. Yet, on the other hand, reason is more than a neutral problem-solving tool. It is more like an escalator: once we get on it, we are liable to be taken to places that we never expected to reach. In particular, reason enables us to see that others, previously outside the bounds of our moral view, are like us in relevant respects. Excluding them from the sphere of beings to whom we owe moral consideration can then seem arbitrary, or just plain wrong.

Steven Pinker’s recent book “The Better Angels of Our Nature” lends weighty support to this view. Pinker, a professor of psychology at Harvard University, draws on recent research in history, psychology, cognitive science, economics, and sociology to argue that our era is less violent, less cruel, and more peaceful than any previous period of human existence.

The decline in violence holds for families, neighborhoods, tribes, and states. In essence, humans living today are less likely to meet a violent death, or to suffer from violence or cruelty at the hands of others, than their predecessors in any previous century.

Many people will doubt this claim. Some hold a rosy view of the simpler, supposedly more placid lives of tribal hunter-gatherers relative to our own. But examination of skeletons found at archaeological sites suggests that as many as 15 percent of prehistoric humans met a violent death at the hands of another person. (For comparison, in the first half of the twentieth century, the two world wars caused a death rate in Europe of not much more than 3 percent.)

Even those tribal peoples extolled by anthropologists as especially “gentle” ― for example, the Semai of Malaysia, the Kung of the Kalahari, and the Central Arctic Inuit ― turn out to have murder rates that are, relative to population, comparable to Detroit, which has one of the highest murder rates in the United States. In Europe, your chance of being murdered is now less than one-tenth, and in some countries only one-fiftieth, of what it would have been had you lived 500 years ago.

Pinker accepts that reason is an important factor underlying the trends that he describes. In support of this claim, he refers to the “Flynn Effect” ― the remarkable finding by the philosopher James Flynn that since IQ tests were first administered, scores have risen considerably. The average IQ is, by definition, 100; but, to achieve that result, raw test results have to be standardized. If the average teenager today took an IQ test in 1910, he or she would score 130, which would be better than 98 percent of those taking the test then.

It is not easy to attribute this rise to improved education, because the aspects of the tests on which scores have risen the most do not require a good vocabulary, or even mathematical ability, but instead assess powers of abstract reasoning.

One theory is that we have gotten better at IQ tests because we live in a more symbol-rich environment. Flynn himself thinks that the spread of the scientific mode of reasoning has played a role.

Pinker argues that enhanced powers of reasoning give us the ability to detach ourselves from our immediate experience and from our personal or parochial perspective, and frame our ideas in more abstract, universal terms. This, in turn, leads to better moral commitments, including avoidance of violence. It is just this kind of reasoning ability that improved during the twentieth century.

So there are grounds to believe that our improved reasoning abilities have enabled us to reduce the influence of those more impulsive elements of our nature that lead to violence. Perhaps this underlies the significant drop in deaths inflicted by war since 1945 ― a decline that has become even steeper over the past 20 years. If so, there would be no denying that we continue to face grave problems, including of course the threat of catastrophic climate change. But there would nonetheless be some reason to hope for moral progress.

By Peter Singer

Peter Singer is professor of bioethics at Princeton University. His books include “Animal Liberation,” “Practical Ethics,” “The Expanding Circle,” and “The Life You Can Save.” For a podcast of this commentary in English, please use this link: http://traffic.libsyn.com/projectsyndicate/singer86.mp3 ― Ed.

(Project Syndicate).