In the BBC News Magazine on 8 January Tom Holland (the author of Islam, The Untold Story) wrote: ‘When Philippe Val, the editor of Charlie Hebdo, published a book in 2008 defending the right of cartoonists to mock religious taboos, the title was telling. He called it Reviens, Voltaire, Ils Sont Devenus Fous (Come Back, Voltaire, They’ve Gone Mad)’. In recent years many of us have been tempted, like M. Val, to call out: ‘Come back, Voltaire, we badly need you!’

‘Once fanaticism has infected the brain, the malady is all but incurable’, writes Voltaire in the Pocket Philosophical Dictionary. Pressing home the idea that fanaticism is a kind of illness, he says: ‘fanatics are people whose madness is fuelled by murder; those who assassinated Henri IV and so many others were sick people, all suffering from the same mad rage’. Speaking of a fanatical sect he’d watched at close quarters becoming ‘more and more agitated’, he notes that ‘their eyes blazed, their limbs shook, and their faces grew ugly with rage’. He adds, as if foreseeing the murders in the Charlie Hebdo offices, ‘they would have killed anyone who dared gainsay them’.

The murder of Henri IV by Ravaillac in the Rue de la Ferronerie on 14 May 1610. Source: Gallica.bnf.fr / Bibliothèque nationale de France, département Arsenal, EST-368 (70)

In a particularly arresting phrase he claims that there is no defence against this ‘bubonic plague of the spirit’. Faith is least effective of all: ‘far from being health-giving nourishment for the soul, in infected brains religion morphs into a poison’. Indeed, it’s hard to see the minds of the authors of the massacre in the Rue Serpollet as other than poisoned.

Being a man of his time Voltaire believed, rather optimistically, that the only antidote to this poison was philosophy. The cure for such an illness, he says, ‘is the philosophical cast of mind, which eventually makes us gentler in our ways’. I don’t know whether the assassins of the Charlie Hebdo cartoonists left their French school before the final year in which philosophie is a compulsory subject. If they did complete the course, it doesn’t appear to have cured them of the ‘poison’ of fanaticism, and it patently failed to make them ‘gentler in their ways’.

Voltaire would have approved of Dan Hodges’s defence of secularism. We must break, Hodges said, ‘the anachronistic link between church and state’, because when it comes to setting boundaries between what can be said – or drawn – and what cannot, we must ensure that they are set not by gods, but by ourselves.

– John Fletcher

John Fletcher is the translator of Voltaire’s Pocket Philosophical Dictionary.