André Gorz, who has committed suicide, aged 84, together with his incurably ill wife, was one of the leading social philosophers of the 20th century and a pioneer of political ecology. A member of the editorial committee (1961-74) of Jean-Paul Sartre's Les Temps Modernes, and a co-founder of the leftwing weekly Le Nouvel Observateur, he was also associated for a time with the ecological bi-monthly Le Sauvage, where many of the articles collected in the groundbreaking Ecology As Politics (1975) were published.

He argued that a meaningful political ecology must imply a critique of economic thought in general, on the basis that any adequate conception of wealth must necessarily exceed the economist's impoverished notion of "value". This thread ran through his later writings, which focused particularly on questions of the transformation of work and working time, envisaging the possibility that the productivity gains made possible by capitalism could be used to enhance individual and social life, rather than intensifying ruthless economic competition and social division.

In books such as Farewell to the Working Class (1982), Paths to Paradise (1985), Critique of Economic Reason (1988), Reclaiming Work (2000) and the as yet untranslated L'Immatériel, Gorz argued that we are in the grip of a system that is abolishing work as we know it: the problem was not the destruction of employment as such, but the new system's irrational efforts to perpetuate the ideology of work as a source of rights - and, most importantly, of the right to an income. Despite Gorz's longstanding links with trade unions, he increasingly looked beyond the traditional Marxian proletariat to implement his "radically reformist" programme, which advocated a mass exodus from the employment relationship and from commodity-based social relations.

Born Gerhard Hirsch in Vienna, the son of a Jewish merchant and a Catholic secretary, he had his name changed to Horst in 1930 when he was seven, on his father's conversion to his mother's religion. After escaping Austria in 1939, the year after its annexation by Nazi Germany, he studied throughout the war in Lausanne, where he exchanged the German language for French and acquired a diploma in chemical engineering.

A fascination with Sartre's philo-sophy - notably reflected in his first published work The Traitor (1958) - led to their meeting in 1946, and the two remained close until the mid-1970s. In 1949, Gorz moved to Paris with his English wife Dorine, whom he had met in Switzerland, where she was working as an actor. He worked for the World Citizen Movement, a utopian organisation advocating world government, before beginning, in 1952, a journalistic career with Paris-Presse, as Michel Bosquet. Under that name, he went on to enjoy a fearless reputation at L'Express (1955-64) and Le Nouvel Observateur.

But it was as André Gorz - a pseudonym taken from the name stamped on his father's Austro-Hungarian army field-glasses - that he wrote for Les Temps Modernes and published theoretical works, such as Stratégie Ouvrière et Néo-Capitalisme (1964), a blueprint for socialist action, which had a major influence on the Italian and German left.

The Paris events of May 1968 confirmed his belief in the possibility of a convergence between his humanist vision of socialism, based on the pursuit of individual autonomy, and the emancipatory aims of wider social movements. He was also instrumental at this time in introducing the writings of his friends Herbert Marcuse and Ivan Illich to a French audience that was to be singularly receptive to their ideas.

The fractious years after 1968 saw internal conflict at Les Temps Modernes: Gorz resigned in 1974. At about the same time, his opposition to the nuclear industry led to conflicts with the Nouvel Observateur management, his exit from that magazine, and a more marked turn to ecological politics.

His last book was, in many respects, an extended love letter to his staunch ally Dorine, who had for many years suffered from a debilitating, initially misdiagnosed, arachnoiditis. Lettre à D, a surprise commercial success of 2006-07, enabled Gorz to repay a debt which he felt he had incurred by distorting Dorine's portrait in his early Sartrean writings. In it he also announced that the two of them had decided they did not wish to outlive each other.

They were discovered lying side by side. Friends received notification of the death in the following terms: "Gérard Horst and his wife Dorine have united in death as they were united for life." Nicolas Sarkozy hailed Gorz "as a great figure of the intellectual left". Locals in the couple's village described them as simple, welcoming people. I suspect my unassuming friend would have found the latter tribute the more touching.

· André Gorz (Gérard Horst, Michel Bosquet), philosopher, born February 1923; died September 22 2007