A prolific expert on the Enlightenment, Jonathan Israel tends to produce books of daunting length, so this is relatively short at about 240 pages. He is keen to prove that historians have tended to neglect, even deny, the profound ideological influence of radical Enlightenment C18 thinkers on the outbreak of the French Revolution. Only the diffusion of works by such writers as Diderot and d'Holbach, designed to achieve a revolution of ideas as the first step to real change, can explain the events triggered by the meeting of the Estates General in 1789.
Jonathan Israel explores in detail the "irreconcilable" division between the Radical and Moderate Enlightenments. The former believed in the use of reason, with a secular morality divorced from the distorting effects of superstitious religions, although some radical thinkers appreciated ethical Christian teaching. They called for equality, which required a representative democracy, freed from the self-seeking tyranny of kings and aristocrats, for tolerance and freedom of expression. To the moderates, this was at best over-optimistic and naïve. Tradition and the existing order were essential to maintain the fabric of society and God-given moral values. It is interesting to realise that the revered Voltaire belonged to this camp, corresponding with Frederick the Great of Prussia to deplore the idea of giving "enlightenment" to ordinary people who would be unable to cope with it. Similarly, the "moderate" Locke's support for the equality of the soul but not of physical status, meant that he could invest in the North American slave trade with a clear conscience and advocate the establishment of a new nobility in the Carolinas.
Ironically, members of the Counter-Enlightenment converged with the bloody French dictator Robespierre in condemning the Radical Enlightenment as a clinical, mechanistic approach to society, seeking to subvert natural human sentiment.
Frequent convoluted sentences and condensed ideas together with a tendency to list philosophers or their works call for prior knowledge and make for a challenging read. I found the best way to deal with the book was to skim through once for an overview, and then to work back through more slowly to grasp some of the more complex ideas, such as Spinoza's controversial and fundamental theory that mind and body are "one substance" or material, thus "reducing God and nature to the same thing, excluding all miracles and spirits separate from bodies, and evoking reason as the soul guide to human life, jettisoning tradition".
The result is that I have learned a good deal about the complexity of the Enlightenment and the conflicting ideas of its main protagonists. Writers on this fascinating theme tend to focus on different aspects, presenting contrasting views of philosophers and ranging over a wide field in a discursive and often confusing fashion, so piecing one's knowledge together from a variety of sources feels like gluing together a collection of shattered pots with intriguing designs.