Mencken: The American iconoclast, by Marion Elizabeth Rodgers

Over the past five years - thanks to the presence of a born-again Christian in the White House - the United States has witnessed a campaign of intimidation against the secular state by a newly-empowered force in the American body politic: the Bible Thumpers. Of course, the polite, politically correct term for these idiots would be "Fundamentalist Christians". But like many an angry East Coast liberal, I am appalled by the attempts of these purveyors of gimcrack sanctity to alter the doctrine of the separation of church and state that is central to our temporal, democratic life. So let's discard the "tread gently" approach of much of the American media these days, and call these people what they really are: self-satisfied religious fanatics who consider the US to be God's Preferred Terrain.

When you have a clown as President who informs the public that he has two fathers (his biological dad and the Man Upstairs), and when you have a ferociously fought campaign to have Intelligent Design (translation: Genesis 1.1) taught alongside Darwinism in certain state school systems, any sensible and literate American must also start to wonder: where the hell is H L Mencken to vituperate these antediluvian purveyors of pious platitudes?

I think that Mencken (1880-1956) would have approved of such extravagant phraseology, especially when directed against the religious right. Because Baltimore's most famous native son - and perhaps America's best known journalistic disturber of the peace - spent much of his career railing with great stylistic extravagance against the absurdities of the country's religious "mountebanks" (one of his favourite words), not to mention the entire doctrine of America the Righteous.

Consider his statement that "We posture as apostles of fair play, as good sportsmen, as professional knights-errant - and throw beer bottles at the umpire when he refuses to cheat for our side... We deafen the world with out whoops for liberty - and submit to laws that destroy our most sacred rights... We play policeman and Sunday-school superintendent to half of Christiandom - and lynch a darky every two days in our backyard". That antiquated, pejorative expression for an African-American - especially seen within the context of his literate rant against American hypocrisy - points up the manifold contradictions in the person of Henry Louis Mencken.

In one corner, there was Mencken the excessively gifted wordsmith who railed against specious patriotism and all-American conformism, and our underlying Puritan tendencies. This was best exemplified during his lifetime by that inane experiment in national temperance, Prohibition, which he regarded as a complete infringement on personal rights, especially as he once called booze "the greatest of all the Devil's inventions". In the same corner there was the Mencken who helped turn The Smart Set into one of the most influential literary journals of the early 20th century. This was the Mencken who first published several of Joyce's Dubliners stories in the US, who gave F Scott Fitzgerald one of his first literary breaks, who championed that exponent of American naturalism, Theodore Dreiser, and who promoted the work of Sinclair Lewis and his acidic perspectives on small-town life (Main Street) and corporate-class conformism (Babbit).

In the other corner was the Mencken who used racial epithets even while condemning lynching. As a proud German by origin, he supported the Fatherland during the First World War; he had a rather Victorian attitude to women; and had this to say during the early rise of Nazism: "Hitler seems to be a shabby ass, but I can well understand why so many Germans are supporting him in the present situation." He did revise his opinion once Hitler began to "make speeches worthy of an Imperial Wizard of the Klu Klux Klan".

To the immense credit of Marion Elizabeth Rodgers, this splendid new biography maintains an intelligent critical distance when it comes to Mencken's manifold complexities. More tellingly, Rodgers's exhaustively researched and immensely readable doorstopper of a book does shrewdly show how Mencken's career parallelled the casting-off of America's 19th century parochialism and its emergence as a brash world power. Yet the US simultaneously grappled with its two great demons: its self-righteousness and its obsession with the mercantile.

More than any other writer of the first half of the 20th century, Mencken understood the inherent paradoxes of the American character. He could lambast the unquestioning masses - whom he christened "the booboisie" - as well as the general stupidity of politicians, while leading splendid character assassinations against the likes of William Jennings Bryan (the one-time presidential candidate who prosecuted the Tennessee teacher John Scopes for teaching Darwinism). Mencken decried him as "a poor clod... a peasant come home to the dung-pile".

At the same time, Mencken was also deeply in love with our complex, punchy patois. With The American Language, he wrote one of the first influential books on idiomatic American English. In his work as a literary editor, he was key to fostering a cultural confidence in a still-adolescent nation which, when it came to high art, still cast a nervous backward glance towards Europe.

Rodgers juggles the dense narrative of Mencken's life and times with considerable dexterity, while also providing a glimpse into the very private world of a man who had many mistresses and a pathological fear of domestic entrapment. His was one of the key American literary lives of the 20th century, and Rodgers has, quite simply, done him proud. And, yes, his vitriol has even greater bite in the strange times we inhabit today. To repeat one of his most often quoted statements: "Heave an egg out of a Pullman window, and you will hit a Fundamentalist almost anywhere in the United States today". Plus ça change.

Douglas Kennedy's new novel, 'State of the Union', is published by Hutchinson