Henry Louis Gates Jr. felt the hairs on the back of his neck stand up as he looked across the threshold of his home at police Sgt. James Crowley.

Looking back at Gates, Crowley worried about making it home safely to his wife and three children.

Fear was the only thing the white police officer and black scholar had in common. Soon their many differences would collide, exploding into a colossal misunderstanding.

How could things go so wrong?

How could two by all accounts decent men start a fire that knocked President Obama off his racial tightrope?

Part of the answer lies in the truth seen through each man’s eyes during the episode, which ended with one of the most influential men in the nation charged with disorderly conduct. The charge later was dismissed.

If this really is to become a “teachable moment,” as Obama hopes, then we have to examine what they saw, according to their public statements—and why they saw it that way.

It’s early afternoon in Cambridge, Mass., a few blocks from the campus of Harvard University. Gates and his car service driver, a large black man, are trying to force open Gates’ jammed front door. A woman passing by calls 911.

Gates, 58 and gray-haired, says he was walking with a cane. After they forced open the door, Gates says, the driver carried Gates’ luggage into the house, then drove off.

None of that was on Crowley’s mind when he walked up the steps to Gates’ home.

Crowley is on the porch, alone; Gates is inside his home. They apparently notice each other through the front door window at about the same time.

Crowley sees the unknown: “I really wasn’t sure exactly what I was dealing with,” he said later.

The sergeant, 42, is a decorated 11-year police veteran.

He’s an instructor in a police academy class on how to avoid racial profiling.

He asks Gates to step outside.

Gates, a renowned scholar of black history, has spent most of his life literally cataloging the sins of the past in volumes like “Africana: The Encyclopedia of the African and African American Experience.”

“I know every incident in the history of racism from slavery to Jim Crow segregation,” he said recently.

So when Gates hears Crowley ask him to step outside, he sees history. How could he not?

“All the hairs stood up on the back of my neck, and I realized that I was in danger,” Gates said later. “And I said to him no, out of instinct. I said, ‘No, I will not.’ ”

Crowley asks Gates to prove he lives there.

Looking out his front door, Gates sees someone who should be asking, “Is everything all right, sir?” He sees someone who would not doubt that a 58-year-old, gray-haired Harvard professor lived in this home—if he were white.

Gates sees a racist. Gates leaves the front door to get his identification. Crowley follows him inside. Gates says he provided a driver’s license with the address of the home they were standing in.

Gates demands that the sergeant provide his identification.

Crowley sees someone who should be grateful, but instead is yelling and falsely accusing him of being a racist. He sees “something you wouldn’t expect from anybody that should be grateful that you’re there investigating a report of a crime in progress.”

Neither man understood what the other one saw.

Crowley says he will talk to Gates outside, where he was arrested.

Should Gates have realized that you can’t antagonize the police? Should Crowley have understood what it means to suspect a black man of breaking into his own home? Arguments will persist for years.

Obama said later that both men overreacted.