But the expressions are hardly original to Obama. Bill Clinton referred to “the right side of history” 21 times over his time in office, while his staffers added another 15. Clinton also mentioned the “wrong side of history” several times. Ronald Reagan, for his part, wryly resurrected Leon Trotsky’s relegation of the Mensheviks to the “dustbin” or “ash heap of history.” Speaking to the British Parliament in 1982, the Gipper said, “The march of freedom and democracy which will leave Marxism-Leninism on the ash-heap of history as it has left other tyrannies which stifle the freedom and muzzle the self-expression of the people.” Reagan used both translations of Trotsky’s phrase several more times.

Obama’s own fresh contribution to the genre is his invocation of “the arc of history.” It’s his adaptation of an older phrase, “The arc of the moral universe is long but it bends toward justice,” which was popularized by Martin Luther King Jr. but coined (evidently) a century earlier by Theodore Parker. Obama has mentioned “the arc of history” a dozen times since his election.

The problem with this kind of thinking is that it imputes an agency to history that doesn’t exist. Worse, it assumes that progress is unidirectional. But history is not a moral force in and of itself, and it has no set course. Presuming otherwise embraces the dangerous tendency that the great English historian Herbert Butterfield dissected in his 1931 essay, The Whig Interpretation of History. Butterfield was writing about the inclination among certain historians to see the Reformation as a unalloyedly positive force—a secularizing, liberalizing movement that led inexorably to liberal democracy in the 20th century. Butterfield objected that this wasn’t at all how things worked. It was just a retrospective reading.

“The total result of this method is to impose a certain form upon the whole historical story, and to produce a scheme of general history which is bound to converge beautifully upon the present," he wrote. In fact, “the more we examine the way in which things happen, the more we are driven from the simple to the complex.”

Viewing history from the standpoint of the present not only misrepresented the complexity of events, he wrote, but also risked framing history as a natural progression wherein humans improved over time, going from darker, less intelligent and moral times to an ever-improving present. Butterfield warned against that:

History is all things to all men. She is at the service of good causes and bad. In other words she is a harlot and a hireling, and for this reason she best serves those who suspect her most. Therefore, we must beware even of saying, "History says [...]" or "History proves [...]", as though she herself were the oracle; as though indeed history, once she spoken, had put the matter beyond the range of mere human inquiry. Rather we must say to ourselves: "She will lie to us till the very end of the last cross-examination."

Forget that history doesn’t tell such simple stories and you end up employing this seemingly inexorable progression as evidence that humanity will continue to improve inexorably in the future. Butterfield warned in particular about the temptation to read moral judgments into history, to assume the thrust of events was determined by or proved the validity of reality over alternative possibilities that had not come to pass.