ASPEN, Colo.—Shaka Senghor spent 19 years in prison, including four-and-a-half years in solitary confinement, where he was on lockdown in his cell for 22 or 23 hours a day.

On an Aspen Ideas Festival panel on mass incarceration that began with statistics about the high percentage of citizens that the United States locks up relative to other liberal democracies, Senghor gave a personal view of what it was actually like to be one of those inmates. “Basically it was a big warehouse of young energy,” he said, “young males who come from broken, dysfunctional backgrounds. Fortunately, I came in with a GED. That gave me the opportunity to learn and study."

On his own initiative, he structured his days as if he was in college: “Some of my greatest mentors are still serving life sentences in prison. And they gave me books."

But many fellow inmates in solitary confinement were not literate, and there was nothing in place to give their days structure, or even to keep them sane. “The majority of men that I was around suffered from some kind of mental illness,” he said. “And if they didn't, they eventually succumbed to the madness of the environment.”

Moreover, he observed, most of his fellow inmates had been victimized in some way, whether in their families or on the streets. “I was shot multiple times at the age of 17. I was processed through the hospital, sent home to the same block, no psychotherapy,” he said. “I was convicted for second-degree murder at the age of 19.” He argued that there is an illogic to thinking that further hurting already damaged people, through punishment, could result in their coming out of prison healthy.

“Our responsibility,” he said, “is to determine what kind of men and women we want to return to our community.” And the current American approach, putting inmates in solitary confinement with little effort to rehabilitate them, is “one of the most barbaric and inumane aspects of our society,” he argued. “I call it America's greatest shame.”