In Radical Enlightenment, the great revisionist study which Enlightenment Contested continues, Jonathan Israel made an irrefutable case for the Amsterdam philosopher Baruch Spinoza as the instigator of modern "Western Atlantic" values, with individual liberty, universal equality, democracy and rationalism at its core. A previous notion of the Enlightenment was based on a more moderate programme, associated with Hobbes, Locke and Voltaire.
This was mainstream Enlightenment, dominant in Western thought to 1945. Its moderation diminished the force of the radical rationalism that pre-dated it and gave us the historical modernism which accounts for how we lead lives today - lives, surely, not quite in tune with our more radical hopes. This moderate mainstream Enlightenment was associated with the early to mid 18th century. It sought to accommodate reason and faith, and restrained its criticism of systems less than democratic. Sometimes its spokesmen were impelled by a sense of responsibility for the status quo and concealed their disruptive private view.
Because it accepted the Church, the moderate view disavowed total sexual freedom; because it accepted empire, it sanctioned something less than universal social justice. Latter-day mainstream scholars saw the French Revolution as the outcome of Enlightenment reason. But Israel's account suggests that 1789 gave unexpected life to that radical rationalism which since the mid-17th century became known as "Spinozism". After the event, Spinozism was once more contained by its moderate counterpart. Israel's complex argument becomes clearer in this second volume, and will be finessed in a third encompassing the late 18th century.
It is that Western Atlantic philosophical modernism is distinct from the historical modernism we live. His method traces "how structures of belief and sensibility" interact "with the evolution of philosophical ideas". This technique accounts for the daunting length of these volumes, but suggests how they can be more comfortably read, once the overlapping nature of evidence is clear.
Another welcome aspect of Isarel's revision of this "decisively important" phenomenon, seen by him on a par with the Renaissance and the Reformation, is the conviction that history is moved primarily not by socio-economic forces but by ideas in their social context. The author is professor of intellectual history at Princeton, and his books offer a new foundation for teaching the history of ideas, against the contrary discipline of "social history".
Israel has responded to the decline of the Marxist-influenced human sciences. Yet he is a sophisticated thinker, and understands that Marx is part of the radicalism he is restoring to prominence. We would do well, he suggests, to see the philosophical modernity of the Western Atlantic world as a constant contest between three competing blocs: Radical, Moderate and Counter-Enlightenment. The typical strands of argument recur, as we read our way through a century of journals and follow the arguments in the coffee-houses of Amsterdam. From there controversies spread across Europe, from Poland to Italy, before the "High" Enlightenment climaxed in 18th-century France.
Israel stresses the importance of renouncing the old, recently revived, view of "enlightenments" classified by nation. The true Enlightenment was an unofficial parleyment of nations, in which the leading contributions came from Holland, Britain, France, Germany and Italy.
"Spinozism" took its cue from Spinoza in the way that Marxism derived from Marx. The "ism", often used as a tag of abuse, flattened out and adapted certain basic premises, which in Spinoza's case amounted to materialism and rationalism. His doctrine of "one substance", a challenge to the moderate Descartes' mind-body account of creation, was revolutionary because it denied any role to a divine prime mover. Our natural world, including our humanity, contains all the forces needed to bring about change and progress.
Not all later disciples of Spinoza, especially not pantheists, would see him as an atheist. But that was the political weight his system carried. The implications for a world still ruled by the divine right of kings were staggering. Just like Marxists two centuries later, it became difficult for 17th-century Spinozists to get jobs.
The Spinozist legacy was carried forward by Pierre Bayle in France, and into the High Enlightenment by Diderot, d'Alembert, Condorcet and others. Through the Cold War it was common for scholars to see a link between Spinoza's own system and the dialectical materialism that underpinned Communism. The demise of Communism suggests another reason why the present revision has come about. Israel leaves us in no doubt that it remains a radical vision, "a re-evaluation of all values", with links to Nietzsche and Marx rather more than to Locke and Voltaire.
The meaning of Israel's distinction between radical and moderate enlightenment becomes clear in an example of enormous relevance today. "Religious toleration" is a moderate Enlightenment position, while "freedom of thought" is radical. Diderot suggests that to argue against religion in a tolerant society makes philosophy intolerant. It better serves its purpose by arguing for freedom. Freedom of expression must take precedence over freedom of worship.
With the untarnished force of Spinozism, Israel reminds us of a vision of reason - associated with Europe but drawn from many forces, not least Judaism and Islam - that sets universal standards for progressive mankind. He insists that reason is superior to non-reason, whatever its origin. His thousand-page reminder comes at a time when many of us need a boost to keep up our courage. It is a superb project, and Enlightenment Contested, meticulously produced, deserves space on every thinking person's shelves.
Lesley Chamberlain's latest book is 'The Philosophy Steamer' (Atlantic)