Revolutionary Ideas: An Intellectual History of the French Revolution from The Rights of Man to Robespierre, by Jonathan Israel, Princeton RRP£27.95 / $39.95, 888 pages

In August 1793, four years after the fall of the Bastille, the Tennis Court Oath and the Declaration of the Rights of Man and of the Citizen, and just seven months after the execution of Louis XVI, a democratic constitution for France was proposed. It represented a flowering of Enlightenment rationalism, balancing radical ideas of popular sovereignty with a pragmatic recognition of the need for a system of representative government.

Yet by October, with enemies all around, the constitution had been set aside as the French government declared itself “revolutionary until the peace”; a warrant was put out for the arrest of the Marquis de Condorcet, a philosopher and mathematician who had been one of its principal engineers. He would take his own life around five months later.

After Condorcet’s Girondin faction was pushed aside by the Montagnards, the Revolution took a different course into Terror, with the “incorruptible” Robespierre ruling through the Committee of Public Safety until the coup of 9 Thermidor (or July 27) 1794. Thermidorean reaction would see Robespierre executed the next day, and a new period of rule established under the Directory. Five years later, Napoleon’s dictatorship took power. France’s democratic experiment was over – and yet nothing would ever be the same again.

According to this hefty new study of the French Revolution by Jonathan Israel, a professor of history at Princeton, what such events really show is the motivating power of ideas in guiding and transforming events. In his terms, the French Revolution was a “revolution of ideas” before it became “a revolution of fact”; indeed, it was three revolutions all at once.

Ideas about political equality, anticlericalism and modern republicanism grounded in “reason” motivated Radical Enlightenment thinkers such as Condorcet and Thomas Paine, while they clashed with the “moderate Enlightenment constitutional monarchism” embodied by more pro-royalist factions (the Feuillants) and aristocratic supporters such as Lafayette. Both struggled against Robespierre’s “authoritarian populism”, which for Israel prefigures modern fascism.

The radical compound in this instance might have been uniquely French but its impact spread widely. The resounding Declaration of the Rights of Man, writes Israel, was a “manifesto entirely incompatible with all ancien régime notions of social, racial, and religious hierarchy”. Revolution lent support to Caribbean struggles for black emancipation such as that of Toussaint L’Ouverture in Haiti, memorably described in CLR James’s 1938 classic The Black Jacobins. James’s book, however, is an odd omission in Israel’s otherwise compendious bibliography.

In Revolutionary Ideas, Israel continues to develop a theme that started as a minor moment in his 1995 book The Dutch Republic: Its Rise, Greatness and Fall. There, what he terms “Radical Enlightenment” begins around the 1640s and 1650s, when Dutch republicans start arguing that self-government and freedom of expression require the elimination of religious authority. In particular, Israel focuses on how the Dutch-Jewish philosopher Benedict Spinoza gave such ideas philosophically defensible form, allowing republican politics and religious toleration to be brought under a “monist” and materialist explanation of the structure of the world. For Spinoza, very baldly stated, God is identical with nature, so that nature as God constitutes the singular substance of the world.

What Israel sees as Spinoza’s rejection of political hierarchy and his defence of a democratic republicanism comes through an understanding of man as part of that nature. Toleration flows from such natural or substantial equality, and once these ideas from the Dutch Republic take off and circulate, Israel is able to trace their history and impact as they rise and fall from the scientific revolution to the age of the rights of man. In a series of monumental books, Radical Enlightenment (2001), Enlightenment Contested (2006) and Democratic Enlightenment (2011), a similar argumentative structure emerges: Spinoza’s true heirs do battle with reaction, occasionally winning, sometimes losing but always cultivating freedom of expression. At the same time, Radical Enlightenment does battle with moderate and sceptical forms of enlightened philosophy such as that proposed by the wine-selling Bordeaux philosophe, Baron de Montesquieu, or the work of Scottish theorists of commercial society such as David Hume and Adam Smith.

For Israel, resurrecting the Radical Enlightenment is part of a project designed to save the Enlightenment more generally. Both as a moment and as a political project, he thinks it must be rescued from political relativism under the guise of academic postmodernism. He also wants to salvage the French Revolution and its connections to Radical as well as moderate Enlightenment from generations of Marxist historians who see it simply in terms of class conflict, as well as their revisionist liberal critics, who see the logic of terror inscribed into revolutionary catechisms from the outset.

Israel writes that historians of the French Revolution “have a problem” in that they have never agreed on a single major cause for its outbreak. He ends Revolutionary Ideas with a ringing affirmation of what he believes this to be: “Radical Enlightenment alone offered a package of values sufficiently universal, secular, and egalitarian to set in motion the forces of a broad, general emancipation based on reason, freedom of thought, and democracy.”

Historians have often criticised Israel for flattening out all the differences between these radical ideas except those he wants to retain and, when applied to the French Revolution, his arguments can feel like the inverse of some 19th-century Marxist schema. Instead of subterranean economic determinations, it is Radical Enlightenment that provides the means by which everything from press freedom to de-Christianisation can be slotted into a matrix requiring little in the way of extra interpretation.

What you get from such a focus on subversive editors, disenchanted priests and materialist philosophers has much in common with a more conventional account: food shortages, public debt crises and social grievances from Paris to the Vendée, combined with a plethora of radical ideas about press freedom, absolute equality, political liberty and radical democracy. Yet the vaulting ambition to ascribe such a momentous transformation to one cause still feels hubristic. The obvious parallel in this year of all years would be the thought that there might be a single idea or singular complex of ideas behind the outbreak of the first world war. Can you imagine such a claim commanding general assent?

Duncan Kelly teaches political thought at the University of Cambridge