Jerry Cohen was one of the liveliest and most imaginative minds — and wittiest lecturers — in the international philosophical community. He was best known as a leading contributor to the analytical Marxism movement of the 1980s, But when he finally acknowledged that the Marxist project was beyond rescue, he spent the rest of his career defending the egalitarian morality that he always thought was the heart of Marx’s criticisms of the unjust, arbitrary and irrational capitalist system. The culmination of those efforts, Rescuing Justice and Equality, appeared in 2008, but the brief and very accessible Why Not Socialism? will now appear posthumously in the autumn.

Like his immediate predecessor as the Chichele Professor of Social and Political Theory at the University of Oxford, Gerald Allan Cohen was born and educated in Montreal. There, the similarities end. Charles Taylor embodied the two founding cultures of his home city, French and Scottish, while Cohen recalled that he was 10 years old before he realised that there were some people who were neither Jews nor communists.

Born in 1941 and educated at Morris Winchevsky Jewish School, Strathcona Academy, Outremont High School and McGill University, Cohen came to Oxford in 1961 to take the BPhil in philosophy.

Philosophy in Oxford was no longer dominated by the austerities of J. L. Austin, but it was nonetheless committed to the kind of analytical programme that almost all Marxists despised. Cohen’s career was for two decades built on the conviction that the insights of Marx could be explained and defended with the weapons of analytical philosophy. At Oxford he was taught by Gilbert Ryle and Isaiah Berlin. It was Ryle’s philosophical weapons that he employed in the unlikely cause of defending Marx, rather than Berlin’s talent for storytelling. Nonetheless, Berlin became a close and helpful friend. As Cohen told the story during his valedictory lecture on retiring from the Chichele chair in 2008, that friendship led to the first of the two academic posts he held in this country.

The head of the philosophy department at University College London, Richard Wollheim, an old friend of Berlin’s, was introduced to Cohen on a visit to Oxford. When Cohen said he had no idea what he was going to do next, Wollheim offered him a lecturership. He spent the next two decades in one of the liveliest departments in the English-speaking world, where he not only honed the ideas that made analytical Marxism a formidable intellectual force, but developed a passion for the visual arts.

In 1978 he published his most influential book, Karl Marx’s Theory of History: A Defence. It was a defence of orthodox Marxism, that is to say of a form of economic determinism. Cohen describes how forces of production dictate relations of production, which in turn dictate legal and political arrangements, and how history is the history of the development of our productive capacity, driven by conflicts over the distribution of the proceeds of our efforts.

It was a stunningly clever work. Much of its ingenuity was directed against the familiar objection that it is impossible to distinguish between the so-called base and superstructure of Marx’s theory. But the most controversial and most sophisticated, if in the end a not wholly successful, argument was the defence of functional arguments in social science.

Marx had claimed that social relationships developed as they did in order to promote the development of productive forces; so functional claims of this sort had to be rescued from the near-universal obloquy of critics. By the 1960s functional explanations had come to be disliked both for political and intellectual reasons; they seemed superstitious, and to embody a conservative view of the world, propped up by appealing to the good effects of institutions that the Left disliked — the Church, the monarchy, the nuclear family. Cohen’s achievement was to show that what he called “consequence explanations”, in which events were explained by the consequences they brought about, were perfectly respectable.

In 1984 Cohen was elected to the Chichele Professorship of Social and Political Theory, and took up the chair in early 1985. He was elected to the British Academy also that year. His tenure of his chair was as long as that of his three immediate predecessors combined. (Isaiah Berlin had moved on to found Wolfson College, John Plamenatz had died in his early sixties, and Charles Taylor left to play an active role in Canadian politics.)

Cohen’s 24-year tenure gave a distinctive cast to Oxford political theory, emphasising its connections with contemporary moral philosophy, in contrast to the more historical and institutional style of the Cambridge of Quentin Skinner and John Dunn.

Although the support of Berlin and Wollheim had been important in his election, it was somewhat surprising that Cohen was tempted away from London. Oxford in general, and All Souls in particular, did not look like the natural habitat of someone who still thought of himself as a Marxist.

In fact Cohen found himself surprisingly happy at All Souls; he enjoyed the company not only of the local philosophers such as Derek Parfit and Leszek Kolakowski, but that of the endless stream of visitors to All Souls and Oxford. In any case he was at the centre of a group of like-minded political thinkers in Europe and the United States, including Jon Elster, John Roemer, Adam Przeworksi, Erik Olin Wright, and Philippe van Parijs. Not all of them were Marxists, but they were all concerned with Marx’s own concerns, especially issues of class, justice and exploitation.

Cohen was much in demand as a lecturer; the combination of personal charm, a wit that made difficult philosophical points intelligible, and a determination to fight off every anti-egalitarian political position he encountered, was irresistible.

His Tanner Lectures, given at Stanford in 1991, argued that writers such as John Rawls had been wrong to make concessions to the supposed selfishness of human nature, and that a just society could only be built on every individual’s commitment to justice. This claim raises an obvious question, tackled in his Gifford Lectures of 1995 and the engaging book that resulted: If You’re an Egalitarian, How Come You’re So Rich?

Cohen spent many years polishing what became Rescuing Justice and Equality. It is an immensely accomplished piece of work. Its virtues are likely to be appreciated mostly by philosophers who share Cohen’s taste for the detailed unpicking of the paradoxes that lurk in most statements of egalitarian principle.

But there is more to it than that. Years before, Cohen had insisted that socialists must make a moral case for socialism, and that the Marxist belief in the inevitability of socialism was absurd. Cohen’s morality was the intuitive conviction that inequality is just wrong.

The slogan that Marx borrowed from St Simon: “From each according to capacity; to each according to need” was what remained when Marxism’s claims to scientific infallibility had been rejected.

Cohen sometimes suggested that his egalitarianism was the product of his Montreal childhood, and sometimes that it rested on a moral intuition as unshakeable as our mathematical intuitions. Wherever it came from, it provided a sense of moral urgency as impressive as the intelligence to which it was allied.

Cohen was twice married: first, in 1965, to Margaret Pearce, with whom he had a son and two daughters; secondly, in 1999, to Michèle Jacottet.

Gerald Cohen, philosopher, was born on April 14, 1941. He died after a stroke on August 5, 2009, aged 68