Norberto Bobbio, who has died aged 94, was Italy's leading legal and political philosopher, and one of the most authoritative figures in his country's politics.
Bobbio's life and work were conditioned by the vicissitudes of his country's democracy in the 20th century. The experience of fascism, the ideological divisions of the Cold War and the transformation of Italian society during the 1960s and 1970s, which he described so evocatively in his Ideological Profile of Italy in the Twentieth Century (1969), prompted and enriched his passionate defence of the constitutional "rules of the game" against those who denied their relevance or would overturn them for reasons of pragmatic convenience.
Bobbio was born into a relatively wealthy, middle-class Turin family. He has characterised their sympathies as "philo-fascist", regarding fascism as a necessary evil against the supposedly greater danger of Bolshevism. At school and university, however, he became acquainted with many of the leading lights of the largely anti-fascist Turin intelligentsia.
These included the novelists Cesare Pavese and Carlo Levi, his future publisher Giulio Einaudi, the critic Leone Ginsburg and the radical politician Vittorio Foa.
Although Bobbio was not active in resistance, he was led to a position of passive, yet profound, intellectual opposition. However, his stress on the importance of civil and political liberties derived much of its power from his having lived his formative years under a government that had suppressed them - even forcing him to pledge allegiance to the regime to save his job, an action he later deeply regretted.
The fall of Mussolini in September 1943 catapulted Bobbio, with so many of his generation, from total exclusion from political life into active involvement with it. Since the late 1930s he had been associated with the liberal socialist movement, which became part of the Party of Action, the main non-communist resistance grouping. He played a minor role in some clandestine activity against the German occupation and was briefly imprisoned from 1943 to 1944.
Although intellectually influential, the azionisti lacked a popular base, and Bobbio stood unsuccessfully in the 1946 constituent assembly elections, then returning to academic life. However, the party's slogan, "Justice and liberty", captures the central theme of much of his subsequent work - how to unite the liberties beloved of liberals with the socialist demand for social and economic justice. It was this commitment to these twin ideals that made him the perfect critical interlocutor between the Communist Party (CPI) and the various governmental parties gathered around the Christian Democrats, and gave him such influence within political life.
Bobbio had taken degrees in jurisprudence and philosophy at Turin. His first book, The Phenomenological Turn in Social and Legal Philosophy (1934), had been followed by a monograph on The Use of Analogy in Legal Logic (1938) and, in 1944, by a critical study of existentialism, and the first of his books to be translated into English, The Philosophy of Decadence. He taught jurisprudence at the University of Camerino, then at Siena, and was appointed to a chair at Padua in 1940.
In 1948 he replaced his teacher, Gioele Solari, as professor of legal philosophy at Turin, where he remained until 1972. During this period he gradually dissociated himself from the broadly idealist approach to philosophy then dominant in Italian universities.
He set himself the task of elaborating a general theory of the practice and validity of law, breaking with the attempts of most contemporary Italian philosophers to offer a speculative philosophy of the idea and morality of law.
In elaborating his version of legal positivism, Bobbio drew on the writings of Hans Kelsen, whose work he had come across as early as 1932. This research ultimately bore fruit in a number of books based on his Turin lectures, of which the most important are A Theory of Judicial Norms (1958) and A Theory of the Legal Order (1960), and studies of Locke, Kant and legal positivism.
Bobbio's legal studies fed into his political writings. Influenced again by Kelsen, he adopted a procedural view of democracy as consisting of certain minimal "rules of the game", such as regular elections, free competition between parties, equal votes and majority rule.
Bobbio's shift from a pure theory of law to a concern with its political embodiment was marked by his moving to a chair in the newly created faculty of political science in Turin in 1972, where he remained until the then statutory retirement age of 75 in 1984. The essays from this period were later collected as The Future of Democracy: A Defence of The Rules of the Game (1984), State, Government and Society (1985) and The Age of Rights (1990), all of which appeared in English.
His prime concerns, from the 1950s onwards, were to enter into dialogue with the PCI and build a social democratic opposition in Italy. Indeed, the latter could only be achieved if the PCI, the country's largest grouping on the left, could be weaned away from the Soviet Union and converted to liberalism.
It is no accident that Bobbio published the first (and, for some years, the only) Italian study of Karl Popper's The Open Society and Its Enemies as early as 1946; he was a founding member of the European Society of Culture, which had this critical dialogue as a goal. His first book of political essays, Politics and Culture (1955), consisted largely of a debate with the Marxist philosopher Galvano della Volpe, and over whether socialist legality could be based on anything other than the traditional liberal rights.
This theme resurfaced in Bobbio's next major foray into politics, in the 1970s. The spur this time came from the "historic compromise" between the PCI and the Christian Democrats.
Bobbio's interventions challenged the coherence of the Eurocommunist strategy of a third way between liberalism and Soviet communism.
He was an equally harsh critic of the corruption of Italian politics, and of the role of the non-communist Socialist Party, under Bettino Craxi.
Bobbio was also closely associated with the peace movement. His view of the political character of law led him to recognise the need for a political theory of international relations. In a series of groundbreaking essays, he explored the possibility for global forms of democracy to give meaning to international law. He was a passionate critic of nuclear weapons.
He was not a pacifist, though many were surprised when he supported the first Gulf war - a position he defended in his book, A Just War? (1991), but later went back on.
An esteemed political commentator, who wrote regularly for the Turin-based daily La Stampa, Bobbio kept aloof from direct involvement in party politics, and refused invitations to stand as a senator. He took his teaching duties extremely seriously. In the year of his retirement, however, he was nominated by the Italian president to one of the five life senatorships and sat in the upper house as an independent socialist. Indeed, in 1992, he came close to being elected president as a compromise candidate. But he confessed to finding decision-making difficult; his talent was always spotting problems rather than solutions, and he was relieved that the bid failed. He became an outspoken critic of the current prime minister and media magnate Silvio Berlusconi.
Bobbio's wife of 58 years, Valeria, died suddenly in 2001, though three sons survive him. He himself died as he had lived, with great dignity, instructing his doctors not to intervene when he was taken into hospital soon after Christmas. To his credit, he founded no school, while influencing many.
Noberto Bobbio: born October 18th, 1909; died January 9th, 2004