The French historian Pierre Vidal-Naquet, who has died aged 74, was famous for his denunciations of the torture practised by the French army during the Algerian war of independence (1954-62). He was one of the most distinguished contemporary exemplars of the French tradition, dating back to Zola and the Dreyfus Affair (if not indeed to Voltaire), of the intellectual engaged in politics.

Vidal-Naquet was born into a cultivated and bourgeois Jewish family. His father, Lucien, was a lawyer. The Vidal-Naquets had long abandoned religious practice, and like many assimilated French Jewish families, their religion, if they had one, was attachment to the democratic values of the French Republic. Vidal-Naquet's grandfather had been involved in the struggle to prove Dreyfus innocent; his uncle was named Georges (after Georges Picquart, the army officer who had helped uncover the affair), Emile (after Zola), and Alfred (after Dreyfus himself). The moral of the Dreyfus Affair was seen to be that the republic had triumphed over the army; truth over raison d'état.

Pierre remembered his father telling him the Dreyfus story during the German occupation. The family had taken refuge in Marseille and Lucien was excluded from the legal profession by Vichy's anti-semitic laws. From the end of 1942 the Germans occupied the whole of France, and Marseille was no longer safe. On May 15 1944, Pierre's parents were arrested and deported to Auschwitz. Pierre was not at home, and one of his teachers organised some fellow pupils to track the boy down and prevent him returning home. Thanks to this he was saved, with his two brothers and sister, and looked after by Protestant families in the Cévennes. Only after liberation did Pierre understand he would never see his parents again.

He completed his studies, and started a career as a historian of ancient Greece. His first posting was at Caen in 1955, but almost immediately he was catapulted into another parallel existence which absorbed him for years. In 1954 a revolt broke out in Algeria against the French. The French army rapidly resorted to ever dirtier tactics to break the rebels. In June 1957, Maurice Audin, a mathematics lecturer at Algiers University who opposed war, was arrested. Ten days later he disappeared after supposedly escaping from detention.

Vidal-Naquet was suspicious of the army's version of events, and he was one of the founders, in November 1957, of the Maurice Audin committee. In May 1958, Vidal-Naquet published his book, L'Affaire Audin, using his forensic historical training to demolish the official version, and demonstrate that Audin had been murdered by the French army (and probably tortured). His model in this exercise was the 1898 articles of the socialist Jean Jaurés demolishing the trumped up case against Dreyfus.

Thus began for Vidal-Naquet four years of political activism. In 1958 the Audin committee published an article entitled Nous Accusons. In 1960 Vidal-Naquet was one of 121 intellectuals who signed a petition defending the right of insubordination for conscripts called up to fight in Algeria. He testified in September 1960 in defence of Henri Jeanson, who was involved in actively supporting the Algeria rebels. For these activities Vidal-Naquet was suspended from his teaching post for a year in 1959-60.

After the end of the war, he published a Penguin Special, Torture: Cancer of Democracy, which denounced the entire edifice of torture, blaming not only the army, but the politicians who had authorised it (and also brought in cases of British torture in Cyprus and Kenya).

In 1962, Vidal-Naquet returned more fully to his teaching. From 1966 until his retirement in 1997 he taught at the prestigious Parisian École des Hautes Études en Sciences Sociales. He produced original work on the origins of Greek democracy, on Greek slavery and what Greek myths revealed about the social structures of ancient Greek society.

But throughout his life, he continued to make his voice heard in politics, opposing the Vietnam war (he was among the founders in 1966 of the French National Vietnam Committee) and the military dictatorship in Greece. From 1967 he tirelessly advocated the need for a two-state solution in the Middle East. In the late 1970s he also began to turn his attention to the rise of "negationism" in France - the theory that the Nazi gas chambers had not existed - and wrote a book denouncing what he called the "assassins of memory". But equally his opposition to state sponsored official history led him to oppose the French law making negationism a crime. His last public act was to sign an appeal in Libération on July 27 criticising Israeli military intervention in Lebanon.

Vidal-Naquet was never in thrall to any particular political movement. Unusually for French intellectuals of his generation he was never a communist. He was motivated by a sense of justice and moral outrage deriving both from the political traditions of his family and the tragic circumstances of his parents' death. He was capable of anger, but unlike other supporters of the Algerian cause, such as Jean-Paul Sartre, he never romanticised the violence of Algerian nationalists. Sometimes he regretted that his passion had led him to exaggerate (for example talking of a genocide in Algeria), and he also came to feel disappointed in the failures of the new Algerian regime. In 1995 he wrote of Algeria: "Between military dictatorship and Islamic terrorism can one still hope that a free society will emerge? I continue to believe it will."

His political commitment was closely embedded in his metier as historian. His self description was: "A man of passion who commits himself, crossed with a historian who watches him closely, or at least should watch him closely."

His first lecture to his students after Charles de Gaulle was brought back to power in 1958 by a military coup was on the relationship between state and army in ancient Greece. He liked to quote a passage by Chateaubriand denouncing silence in the face of state criminality that he had found in his father's diary for 1942: "When in the abjectness of silence, one no longer hears the chains of the slave or the voice of the denouncers, when everyone trembles before the tyrant, the historian appears. It is in vain that Nero triumphs, Tacitus has already been born in the empire."

Vidal-Naquet's death has deprived France of one of the most noble examples of the committed intellectual.

He had three sons with his wife, Genevieve.