It is the first time that Tunisians have been given a state venue to air the horrors of decades of systematic human rights violations under both President Zine el-Abidine Ben Ali, who was overthrown during the Arab Spring, and his predecessor, Habib Bourguiba.

“This is a momentous day for the establishment of the Constitution and the rule of law,” Sihem Bensedrine, the president of the Truth and Dignity Commission, said in an opening speech. “Victims of despotism are entitled to fairness and justice, and this is the message we are conveying to the whole world.”

Over the past two years, the commission has taken in 65,000 complaints from victims — investigating about 10,000 of them so far — but has struggled against political and institutional resistance and a hostile national news media, which has accused it of spending money but doing nothing.

With the public hearings, Ms. Bensedrine said she hoped to win greater public support and push back against the current government’s argument that stability and reconciliation are more important than reopening old wounds.

The audience on Thursday included many politicians and activists who themselves had suffered imprisonment, torture and exile under the dictatorships. There were also representatives of truth commissions from Africa, Asia and Latin America, and foreign diplomats. Senior Tunisian government officials were conspicuously absent.