One of the most indelible images from the O.J. Simpson story came when a TV camera crew set up in a lecture hall at Howard University, a mostly black school. The law school class sat, waiting to hear the verdict in the controversial murder trial. When the not guilty decision was announced, the students — all of whom appeared to be of African descent — burst out of their seats in jubilation, hugging each other and cheering.

The reaction seemed, to nonblacks, bizarre. What could the students possibly be cheering? That a former football player and second-rate actor, who did little for and with his fellow African-Americans, had beaten the odds? Were they cheering the success of the savvy and flamboyant attorney, Johnnie Cochran? Or was it all this and more?

The tragic death of Trayvon Martin, the Sanford, Fla., 17-year-old shot to death by a man acting under the auspices of a neighborhood watch program in a gated community again highlights this perception gap. Though contrary versions of what led to the shooting are now in play, the fact that an unarmed black teen raised the suspicions of a 28-year-old armed man should be troubling to all. And it should shed light on what life is like as a minority.

Too often, nonblacks dismiss the complaints of stereotyping and profiling as paranoia or political grandstanding. Most nonblack Americans do not see themselves as bigoted, so they logically conclude that the complaints are unfounded, or at least exaggerated.

But that’s the heart of this disconnect. Until nonblacks walk in the shoes of people of color, they can never understand what it’s like to be on the receiving end of nervous glances and suspicious questions. Even if Trayvon Martin assaulted George Zimmerman, the man who admitted to shooting the teen, Mr. Zimmerman had already called police about the black teen walking through the gated community before the two had any contact.

This guilty-until-proven-innocent reaction is evidence of a serious divide in our society. From time to time, we are confronted with this divide and reminded of its pervasiveness and corrosiveness.

Often, there is an economic component. When the economy sours, the poor become more desperate, the middle class and working poor become more resentful of those receiving state assistance and the rich become suspicious of class unrest.

And, of course, there is often a political component to these fissures in the social fabric. Florida adopted a “Stand Your Ground” law which Mr. Zimmerman relied upon to protect him from his actions. The law, as it has been explained in news reports, allows people to use deadly force against someone they perceive to be threatening.

New York Times columnist Paul Krugman asserts that the language of this law was not generated by a frightened populace worried about facing legal problems for defending itself from marauding criminals. Rather, the columnist writes, its language is similar to that drafted by ALEC, the American Legislative Exchange Council, the conservative think-tank that has provided templates for laws in many state legislatures, including Maine’s.

Ultimately, legislators are responsible for the bills they approve, and so ALEC and its counterparts on the right and left should not be demonized. But the fact that a conservative think-tank has on its agenda a law to provide cover for would-be vigilantes speaks of a more profound divide than that between blacks and whites, haves and have nots.

The Trayvon Martin story may be an aberration, or it may be more evidence that our society is focused less on what we have in common and more on what divides us.