Here are the core lessons from a book that Mark Zuckerberg and Bill Gates think everyone should read

In today's post-9/11 world, the threat of terrorism looms large for many people.

These fears are fueled by a 24-hour news cycle that sheds light on horrors throughout the world, despite that violence has actually declined.

This dichotomy is one of the reasons that Facebook CEO Mark Zuckerberg chose Harvard psychologist Steven Pinker's "The Better Angels of Our Nature: Why Violence Has Declined" as the second selection in his "A Year in Books" book club.

Zuckerberg writes on his personal Facebook page that, "It's a timely book about how and why violence has steadily decreased throughout our history, and how we can continue this trend."

Bill Gates is another prominent fan of this data-rich, 800-page book. In a 2012 blog post, he wrote that it "stands out as one of the most important books I've read - not just this year, but ever."

Pinker tells Business Insider he wanted to give readers "a different appreciation of the world from day-to-day journalism. Since there will always be incidents to fill the news, if you get your appreciation of the world from the news, you'll get a systematically distorted picture."

"By virtually every measure, the world has become less violent," says Pinker. "Of course that doesn't mean violence has disappeared, just that it occurs at lesser rates than it used to."

To fully appreciate Pinker's book, you'll need to spend a considerable amount of time with it. Here's a breakdown of its main points.

There are six major trends in human history's retreat from violence.

1. The Pacification Process

Around 5,000 years ago, humans made the transition "from the anarchy of the hunting, gathering, and horticultural societies in which our species spent most of its evolutionary history to the first agricultural civilizations with cities and governments," Pinker writes.

2. The Civilizing Process

Between the late Middle Ages and the 20th century, homicide reduced drastically in societies, which sociologist Norbert Elias says is best seen in European countries, in which there was "the consolidation of a patchwork of feudal territories into large kingdoms with centralized authority and an infrastructure of commerce," Pinker says.

3. Humanitarian Revolution

Best understood in the Western world as starting with the Age of Reason and the Enlightenment and lasting hundreds of years, it was the first time there were movements to abolish sanctioned forms of violence like "despotism, slavery, dueling, judicial torture, superstitious killing, sadistic punishment, and cruelty to animals."

4. The Long Peace

At the end of World War II, the world's most powerful and developed countries stopped waging war with each other.

5. The New Peace

Pinker writes that some readers will be surprised to learn that "since the end of the Cold War in 1989, organized conflicts of all kinds - civil wars, genocides, repression by autocratic governments, and terrorist attacks - have declined throughout the world."

6. The Rights Revolutions

Since the late 1950s, there has a been "a growing revulsion against aggression on smaller scales," empowered by movements for "civil rights, women's rights, children's rights, gay rights, and animal rights."

Humans are neither innately good nor innately evil, but have biological triggers that can orient them toward aggression or cooperation.

Pinker's 2002 book "The Blank Slate" argues that the evolution of the brain disproves the "blank slate" theory that lends total moral authority to nurture over nature. In "The Better Angels of Our Nature," Pinker categorizes "five inner demons" as psychological systems that can be triggered to release aggression, along with "four better angels" as motives that can bring humans toward cooperation and altruism.

Pinker clarifies that even though many people have an implicit belief that aggression is something built up with the need to be released, "Nothing could be further from a contemporary scientific understanding of the psychology of violence," he writes.

There are five external factors that favor our "better angels" and have made humans less violent.

1. The Leviathan

A government and legal system with authority on the legitimate use of force compels individuals to refrain from acting on aggressive urges.

2. Commerce

"[A]s technological progress allows the exchange of goods and ideas over longer distances and among larger groups of trading partners, other people become more valuable alive than dead, and they are less likely to become targets of demonization and dehumanization," Pinker writes.

3. Feminization

Pinker argues that "since violence is largely a male pastime, cultures that empower women tend to move away from the glorification of violence and are less likely to breed dangerous subcultures of rootless young men."

4. Cosmopolitanism

Literacy, mobility, and mass media can allow individuals to empathize with people unlike themselves, Pinker says.

5. The escalator of reason

When humans increasingly prioritize reason, they can recognize the "futility of cycles of violence" and selfishness, and can "reframe violence as a problem to be solved rather than a contest to be won," he writes.

Zuckerberg says that he wants people to read Pinker's book because "recent events might make it seem like violence and terrorism are more common than ever, so it's worth understanding that all violence - even terrorism - is actually decreasing over time. If we understand how we are achieving this, we can continue our path towards peace."

"A Year in Books" so far:

• "The End of Power: From Boardrooms to Battlefields and Churches to States, Why Being In Charge Isn?t What It Used to Be" by Moisés Naím
• "The Better Angels of Our Nature: Why Violence Has Declined" by Steven Pinker
• "Gang Leader for a Day: A Rogue Sociologist Takes to the Streets" by Sudhir Venkatesh