The best of all possible words

When Zozo visited England in 17, he was overwhelmed by the grandeur of Sir Isaac Newton's funeral procession. "He was buried," the French exile reported, "like a king who had done well by his subjects."

Better known as Voltaire (a rebranding that still perplexes scholars arguing fruitlessly about the origins of this striking pseudonym), by the time Zozo died more than 60 years later he had himself acquired the trappings of royalty. Choosing to celebrate the Christian name he had abandoned, every St Francis's day Voltaire emerged from his country retreat to inspect a parade of soldiers and receive the homage of admirers dressed up as shepherds; he was also eventually crowned - with a laurel wreath at a performance of his own play.

His death was less regal. After his heart and brain had been removed, Voltaire's body was taken to his estate near Geneva, smuggled out of Paris fully dressed and tied upright in his star-spangled carriage. When it became clear that the projected journey was impossibly long, Voltaire was laid to rest in a decrepit monastery, his freshly recruited mourners distracted by the croaking frogs in the surrounding marshes. But after Louis XVI was deposed, the sceptical rebel who had championed Newton was taken to the Panthéon, France's secular equivalent of Westminster Abbey: he had finally obtained a ceremony as splendid as his hero's.

Such combinations of aspiration, farce and glory characterise Voltaire Almighty , a high-spirited, wide-ranging and empathetic biography by Roger Pearson. He set himself a daunting task: Voltaire wrote about 15 million words, but even this colossal output is dwarfed by the secondary literature generated during a quarter-millennium of hagiography, invective and scholarly appraisal. Pearson, an Oxford professor who is an expert on Voltaire's moral tales, takes a chronological approach, focusing on Voltaire's life and interspersing brief plot summaries as he progresses steadily from cradle to grave. These 400 pages are crammed with facts and background details, and sizzle with personal dilemmas, political conflicts and intellectual ideas. In addition - and far more difficult to carry off - Pearson has used style to convey the flavour of Enlightenment life. By varying his sentence lengths, he avoids the sleep-inducing plod through the decades that typifies so many biographies; by gently mocking his characters, he replicates their own ironic detachment; and by vacillating between subtle pithiness and nudge-nudge sexual allusions, he emulates the occasionally wearing salon humour of 18th-century wits.

In contrast with prevailing stereotypes, the Voltaire who emerges from these pages is neither a philosophical paragon nor a dissolute atheist, but instead is refreshingly vulnerable and altruistic, an emotional optimist who self-protectively hides behind a mask of cynicism. Only through attack can he reveal his true self: after accusing Jean-Jacques Rousseau of writing for the sake of it, Voltaire declared aggressively: "Me, I write to get things done" - thus pre-empting Karl Marx.

Contradictions abound. Living by his rationalist credo, the committed pacifist built up his fortune by investing in military equipment; but by forgoing his royalties, he earned the loyalty of the French theatre. The debonair playwright who transfixed audiences proved incapable of devising a satisfactory plot to control his own affairs, repeatedly offending the patrons he was trying to impress and unwarily tumbling into snares set by wily enemies. The outspoken social climber remained conventional enough to agree "that for the masses a little learning might be a dangerous thing"; nevertheless, he organised a national campaign to ensure that an unjustly hanged shopkeeper was posthumously pardoned and his family compensated. Pearson's Voltaire is far more troubled by indigestion than by passion. He was a chronic invalid obsessed with his bowels and a serial monogamist, faithful (well, more or less) first to the intellectual but temperamental Emilie du Chtelet and then to his niece Marie-Louise Denis, a less demanding woman who nurtured him for 28 years. Denis's portrait shows a plump, motherly figure clutching the laurel wreath preserved from her uncle-lover's theatrical coronation long after he had died; in contrast, du Châtelet stares provocatively out of the canvas, her dividers poised over the scholarly books that seem ill-matched with the elaborate bows and frills of her low-cut dress.

In describing Voltaire's long-term relationships with these women, Pearson's partisan attitude emerges strongly. After several years of close engagement, biographers presumably end up either loving or hating their subjects; indifference must be an impossible stance to maintain.

When he recounts Voltaire's youth, Pearson adopts the indulgent tone of a fond relative vicariously savouring the folly of this "rascal" who overplayed his hand and landed up in the Bastille for almost a year. Later, he protects Voltaire by casting du Chtelet in the role of sensuous yet officious nanny who concocts devious strategies for holding on to her man and defends her roost by ranting at a house-guest until her victim vomits. Pearson might have marvelled at du Chtelet's formidable commentary on Newton's Principia , which was a far more scholarly book than Voltaire's flawed exposition of Newtonian principles; instead, he snidely calls her "Mme Pompon-Newton" and contrives to make it appear her fault that Voltaire betrayed her with his own niece. But their letters have vanished, probably burnt by her brother-in-law; biographers can but wonder at the devotion exhibited by Voltaire when he not only tolerated du Chtelet's pregnancy by another lover, but also helped to convince her husband that the baby was legitimate. And it was the birth that killed her.

In an inspired epilogue, Pearson explores the limitations of biography as a genre and drops his guard to reveal his opinion of this "hyperactive polymath". By infusing his own sensibilities into the carefully assessed evidence provided by earlier biographies, notably the five-volume study by René Pomeau, Pearson has provided an excellently researched, scintillating account. It should become the definitive English version, despite an endearingly modest invitation to challenge his interpretations: "Voltaire (told) Frederick of Prussia: 'I am a tolerant man, and I consider it a very good thing if people think differently from me.' In that respect the Author resembles his Subject."

Patricia Fara is a fellow of Clare College, Cambridge.