It seems like a simple question with an even simpler answer: We don't know where we are going if we don't know where we're from.
But there is a deeper reason, which is that history allows us to understand our own fallibility and hubris, helping us to approach our shortcomings with some degree of humility.
It also emphasizes that progress is not linear, nor is it irreversible. With every step forward, we can still take two steps back. But if we study history's trajectory and learn from our mistakes, perhaps we can be better attuned to what President Abraham Lincoln called
"the better angels of our nature" in his 1861 inaugural address.
History teaches us that the past is indeed a foreign country, so foreign that even a great scientist like Sir Isaac Newton believed in alchemy
and thought that he might have discovered the Philosopher's Stone, a substance that could purportedly turn iron into gold.
This, of course, was entirely false. But a visitor from the 24th century would likely find some of our most cherished beliefs to be as laughable as Newton's embrace of alchemy is to us.
And just as Newton was both a scientist and an alchemist, the founding fathers declared "we are all created equal" while many of them owned slaves.
Were the founders simply hypocrites? Or were they largely prisoners of their own era? Or maybe a bit of both?
Trying to sort through these hard questions enables us to have empathy, or the ability to put ourselves in the shoes of our forebears.
And what about the American original sin -- slavery? That Thomas Jefferson was also a slaveholder should remind us that the story of human progress is hardly the magnificent, linear journey toward the promised land of peace and justice that we often believe it to be.
President Barack Obama was fond of quoting
Martin Luther King Jr.'s aphorism that "The arc of the moral universe is long, but it bends towards justice."
Progress is fragile and reversible
That said, the case of Weimar Germany reminds us how fragile human progress is. In many ways, Weimar was one of the most liberal polities of the early 20th century, yet it birthed Nazism, which in turn led to the Holocaust.
The Holocaust shows us that one man can be both good and evil, depending on the circumstances he finds himself in. As the American historian Christopher Browning showed in his landmark 1998 study, "Ordinary Men: Reserve Police Battalion 101 and the Final Solution in Poland," it was ordinary Germans who willingly participated in the Holocaust.
And who among us can honestly say that they would have been one of the few Germans who stood up to the Nazis. Almost all of those who did oppose the Nazis perished under ghastly tortures.
History reminds us that the forces of darkness are ever-present in the human soul and that few of us really have the capacity to be heroes.
The power of chance
History also teaches us about the power of chance. Nothing about Hitler's ascent to power -- from an obscure blowhard spouting crackpot racial theories in beer halls in 1920s Munich to becoming the master of much of Europe -- was preordained.
Hitler benefited greatly from those in the German upper class who saw him as a former Army corporal they could manipulate to advance their own interests, while other European leaders such as Neville Chamberlain greatly underestimated Hitler's will to power. The German upper class and leaders of Europe both passed up a number of chances to confront and undermine Hitler before he took control first of Germany and then of continental Europe.
Similarly, the American Revolution could easily have been derailed by General George Washington's foolhardy decision in the spring of 1776 to keep much of his army in Manhattan as a great British fleet of 400 ships -- one of the largest fleets hitherto assembled -- surrounded the island.
The British commander General Sir William Howe's much larger forces of soldiers could have finished off Washington's army in New York, but instead the British general dithered -- allowing Washington to organize a hasty retreat and survive to fight another day.
History isn't a march to the promised land
Americans largely subscribe to the "Whig view
" of history: the belief that our liberal values enshrined in the Constitution are powering us forward to an ever-freer and ever-richer future.
This belief is deeply rooted in a Judeo-Christian conception of history, one in which we are all trying to reach the Promised Land, which some have conflated with the United States itself.
President Ronald Reagan famously described the United States as a "shining city on a hill," which echoed an important 1630 sermon by the Puritan John Winthrop, one of America's first colonists who said
"we shall be as a City upon a Hill."
History warns us, however, that a steady march to the promised land is fallacious -- as much as we all might want to believe in it.
In the summer of 1914, there was arguably no more peaceful, prosperous and well-connected world that had ever existed on earth. Countries were bound together by new trade routes, which were enabled by steam ships, trains and the telegraph. Important strides in public health such as the germ theory of disease and the discovery that cholera was spread by contaminated water had been made in the West. And for a century, since the defeat of Napoleon at Waterloo in 1815, there were no pan-European wars.
None of the great powers thought that the Great War would cause the collapse of the Turkish, Russian, German and Austro-Hungarian empires and would contribute to the eventual dissolution of the British empire. Yet all these monarchies and peoples went into the war with the firm belief that God was on their side. 17 million people died during World War I. The Spanish influenza at the end of that war killed tens of millions more.
It would be deeply ahistorical to believe that we might not face similar problems ourselves.
"History never repeats itself but it rhymes," is an observation sometimes attributed to Mark Twain. The 20th century almost certainly was the peak of American power, but as Americans now face a rising China, history suggests that at some point both China and the United States will end up in some kind of war that will greatly damage both powers.
President Trump's National Security Advisor, Lt. Gen H.R. McMaster, has frequently observed
that "People fight today for the same fundamental reasons the Greek historian Thucydides identified nearly 2,500 years ago: fear, honor and interest."
"Based on the current trajectory, war between the United States and China in the decades ahead is not just possible, but much more likely than recognized at the moment," Harvard political scientist Graham Allison
wrote in 2015. "Indeed, judging by the historical record, war is more likely than not."
Just as the Spanish influenza killed 50 million in the wake of World War I, the fast rate of the warming climate and the rise of antibiotic-resistant super viruses
may also trigger a massive pandemic that we will have scant resistance to.
Current advances in gene editing technologies may also allow states or terrorists to construct viruses that simply wipe out whole categories of humans whom they don't regard as people. Does anyone doubt that if Osama bin Laden had had access to gene editing technologies, he would have used them against his enemies?
Getting it right
We also study the past to understand how great leaders come to grasp and master the currents of history more deeply than others.
British Prime Minister Winston Churchill understood the gathering threat posed by Nazi Germany long before his peers did. And Abraham Lincoln felt that slavery had to end before many of his colleagues did.
George Washington learned from his narrow escape from New York that fighting pitched battles with the British -- the world's then-superpower -- was unlikely to win the war and that he would have to modify his tactics and fight a long war of attrition against them, which is why we can celebrate July Fourth in peace today.
Hopefully we can continue to do so. But history suggests that this is more of an aspiration than a certainty.