Margaret Jacob and Jonathan Israel launched two much-debated versions of the historiographical concept of ‘radical Enlightenment’, with, respectively, The Radical Enlightenment (London: Allen & Unwin, 1981) and Radical Enlightenment (Oxford: Oxford University Press, 2001). In successive sequels, Israel has rewritten the history of the Enlightenment down to 1848. A stocktaking of these epoch-making books was overdue and is welcome. Jacob’s work rests on tireless archival research; Israel’s on truly encyclopaedic reading in many languages. Their essays here, however, illustrate how both rely on key terms which are strategically ambiguous. Both favour ‘subvert’ — but does ‘subversion’ make any real difference, or not? Israel praises ‘democratizing republicanism’ but seems uninterested in the institutional forms corresponding to emancipatory rhetoric. In 1792, the ‘Montagnard authoritarian populist coalition’ appears as if from nowhere. What if authoritarian populism is the real form that vaguely democratic aspirations are bound to assume? If so, perhaps the ‘moderate Enlightenment’ of Voltaire and Hume, which Israel condemns for shabby compromises with entrenched power, deserves more credit, and the ‘radical Enlightenment’ of Raynal, Diderot, and Paine a little less. Meanwhile, Israel chides Jacob for over-estimating Freemasonry; she deplores his obsession with Spinoza. Several subsequent essays take Israel’s radical Enlightenment as a given in investigating intellectual life around 1700: Nancy Levene on Spinoza as materialist; Ian Leask on Spinozism in John Toland’s Origines Judaicae (1709); Charles Develennes on the atheism and republicanism of Jean Meslier (linked by rejecting domination, whether human or divine). Wiep van Bunge shows how radical Enlightenment in the Dutch Republic petered out with the rise of Newtonian physico-theology. Beth Lord questions Israel’s understanding of Spinoza, arguing that he wrongly ascribes to Spinoza a normative understanding of nature and supposes that the equality of all natural entities must, for Spinoza, entail political equality in human society. Further essays consider the wider impact of radical thinking: on women’s emancipation (Jennifer J. Davis), on Sade’s incoherent materialism (Winfried Schröder), on Irish revolutionaries of the 1790s (Ultán Gillen). There is much instruction here, but few surprises. Israel’s neat antitheses are questioned by Eric Palmer, who demonstrates the importance of philosophical abbés and other enlightened Christians, and Felix Wunderlich, who shows how two Göttingen professors somehow combined materialism and Christianity. Focusing on empathy and egalitarianism, Devin J. Vartija cogently questions Israel’s claim that Spinozan philosophical monism necessarily implies political radicalism. The concept of radical Enlightenment comes under intense scrutiny: Frederick Stjernfelt, using Google Ngrams, finds that it became current in nineteenth-century Germany and was introduced to the anglosphere by the émigré Leo Strauss (whose arguments about ‘clandestinity’ Israel seems now to favour); Harvey Chisick shows, quietly but devastatingly, that there is really little difference between the ‘moderate’ Voltaire and the ‘radical’ d’Holbach, and that, far from advocating popular democracy, Enlighteners, including d’Holbach and Diderot, distrusted the ‘people’ and denied equality. It is ironic that the first sustained examination of Israel’s radical Enlightenment should leave the concept in shreds.