In 1946, Albert Einstein stood in front of students at one of the oldest historically black college in the United States and decried the oppression of African Americans.

"There is separation of colored people from white people in the United States. That separation is not a disease of colored people. It is a disease of white people. I do not intend to be quiet about it," he said during a commencement speech at Lincoln University in Pennsylvania.

As a Jewish scientist who experienced anti-Semitism in Germany, Einstein showed deep sympathy for black people in America.

He wandered around black neighborhoods in segregated Princeton, NJ, his home after leaving Germany amid the rise of the Nazis.

He sat on people's porches, chatted with them, and handed out candies to their children and grandchildren.

Einstein had become so entrenched in America's civil rights movement that the FBI placed him under surveillance, collecting nearly 1,500 pages of documents on Einstein by the time he died.

But there's another side to Einstein that perhaps people did not know then.

Travel diaries he wrote during a months-long voyage in the 1920s reveals that in his private moments, the Nobel-winning physicist portrayed people of other races, such as Chinese and Indians, in a stereotypical, dehumanizing way.

Einstein's unfiltered musings about the people he saw and interacted with during his journey show that even the civil rights icon and "paragon" of humanitarianism harbored racist thoughts about those who did not look like him, said Ze'ev Rosenkranz, senior editor and assistant director of the Einstein Papers Project at the California Institute of Technology.

"In published statements, he's usually in favor of civil and human rights and was socially progressive. I'm not saying that he didn't believe in those things," Rosenkranz said, but he added that the words Einstein never intended to be published are in stark contrast with his more-guarded public statements.

That contradiction makes Einstein all the more human, said Rosenkranz, who edited The Travel Diaries of Albert Einstein, published recently by Princeton University Press.

"I'm not apologizing for him or anything … I still feel that the unpleasant remarks are quite shocking, but they do reveal that we all have this darker side to our attitudes and prejudices," he said.

Einstein wrote the travel diaries from October 1922 to March 1923, when he and wife Elsa traveled by ship to the Mediterranean, Sri Lanka, China and Japan.

He wrote every day about his surroundings, at times writing as if he was in a hurry. "Radiant day. Sea quiet, almost windless", he wrote October 12, 1922.

Other times, he was more detailed: "In the evening, wonderful sunset - purple with finely illuminated narrow wind-swept clouds," he wrote on the same day.

He chronicled his observations of people he saw and met, summing up "their personalities and idiosyncrasies in just a few, often humorous or irreverent, words," Rosenkranz wrote in the introduction portion of the travel diary.

The average Japanese, Einstein wrote, is "unproblematic, impersonal, he cheerfully fulfills the social function which befalls him without pretension, but proud of his community and nation. Forsaking his traditional ways in favor of European ones does not undermine his national pride."

While Einstein used male pronouns for deeper reflections about the Japanese, his thoughts about women were more about their physical appearance than their personality.

Japanese women, he wrote as he observed them on the ship, "look ornate and bewildered … Black-eyed, black-haired, large-headed, scurrying."

His reflections about the Chinese, with whom he spent far less time, were more callous, even insulting. Though he called the Chinese "industrious", he also described them as "filthy" and "obtuse".

They're a "peculiar herd-like nation", Einstein wrote, "often more like automatons than people".

He saw them as intellectually inferior, quoting - instead of challenging - Portuguese teachers he met during his travels who claimed that the Chinese "are incapable of being trained to think logically" and "have no talent for mathematics".

There was, as Rosenkranz described, a "healthy dose of extreme misogyny":

I noticed how little difference there is between men and women; I don't understand what kind of fatal attraction Chinese women possess which enthralls the corresponding men to such an extent that they are incapable of defending themselves against the formidable blessing of offspring.

His reflections in the few days he spent in China also reveal Einstein's tendency to perceive foreigners as a threat.

"It would be a pity if these Chinese supplant all other races," he wrote. "For the likes of us the mere thought is unspeakably dreary."

In Colombo, Sri Lanka, he wrote with empathy about the beggars on the streets.

He was "very much ashamed" for his complicity in such "despicable treatment of human beings," he said. But he also was critical of them for being poor, Rosenkranz said. He saw them as inferior people who "live in great filth and considerable stench."

The Indians and Sinhalese in Colombo, Einstein said, "do little" and "need little".

As he traveled in the Levant in the Mediterranean, he described Levantines as a "screaming and gesticulating" group of people "of every shade".

Levantine merchants swarmed the ship, Einstein wrote, transforming the upper deck into a bazaar. He found them both repulsive and beautiful, describing them as "bandit-like" and "filthy", but also "handsome and graceful to look at".

About a decade after his travels, in December 1932, Einstein and his wife left Germany for a three-month trip to the United States.

Adolf Hitler and the Nazi party took over the German government the following month. Einstein didn't return home and stayed in the United States, where he became more aware of the plight of African Americans.

He entrenched himself in the civil rights movement, signed anti-lynching petitions and volunteered to testify as a character witness in the trial of writer and philosopher W.E.B. Du Bois.

"It would be easy to say, yes, he became more enlightened," Rosenkranz said. But whether Einstein's racist views, particularly about the Chinese, had changed, Rosenkranz is not sure.

All of this is to say that our understanding of Einstein misses his complexity as a human being, Rosenkranz said.

"One should emphasize the different elements and contradictory elements in the statements that he made and in his personality," Rosenkranz said. "On one hand, he was very generous and very favorable … But there's also these statements that one should not ignore."

What this says about human nature is that we are complex beings with both enlightened and dark beliefs, Rosenkranz said.

"We generally don't express them, but we might harbor them secretly. This gives us the opportunity to look at ourselves."

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This article was originally published by The Washington Post.