Most biographers are rather circumspect. They do not begin their books enunciating a worldview. But then Paul Johnson, a writer with a global mind, is not about to grovel before genre conventions. James Atlas, editor of the Eminent Lives series, chose Mr. Johnson, no doubt, to write “George Washington: The Founding Father” (HarperCollins, 126 pages, $19.95) because another short biography of Washington is not, strictly speaking, necessary. But Mr. Johnson can be counted on to crack through the biographer’s customary caution and produce something new.

Who but Mr. Johnson, author of a highly partisan and ideological biography of Napoleon, would announce his subject this way: “At the beginning of the twenty-first century, the United States seems set to play the leading part in making the earth secure and democratic. In this immense process, then, Washington played, and still plays, a unique role, both as founding father and exemplar of moderation and wisdom.” Mr. Johnson, author of sweeping accounts of history such as “Modern Times,” tempers his vision only slightly with that four-letter word “seems.”

Mr. Johnson is right about Washington, who not only set the pattern for our presidents but also for the world when he voluntarily relinquished power and retired even as Bonaparte was about to crown himself. And the virtue of having a well thought-out worldview is that the details of the biographical subject’s life resonate as so many notes in the biographer’s historical composition.

Admiring Washington’s politics, Mr. Johnson also does the biographer’s job in providing wonderful details about his subject’s person:

Washington did not like shaking hands, which he regarded as an urban vulgarism, the act of a “citizen,” a word just creeping in from Paris. He never thought of himself as a citizen. When greeting you, he bowed, and a Washington bow was worth having, a gesture of deliberative elegance. He never wore a wig, which he thought unbecoming and a nuisance, but dressed with great care like a well-to-do English squire, powdered his hair neatly, and tied it with a velvet ribbon called a “solitaire.”

What a shock, then, to take up Christopher Hitchens’s “Thomas Jefferson: Author of America” (Harper-Collins, 188 pages, $19.95), the story of a zealot all too smitten with revolutionary chic. Quoting Jefferson on the rampaging Jacobins sets him off starkly from Washington. A defender of the French Revolution, no matter the cost in terror and human lives, Jefferson avows: “My own affections have been deeply wounded by some of the martyrs to the cause, but rather than it should have failed, I would have seen half the world desolated. Were there but an Adam and Eve left in every country, and left free, it would be better than it is now.”

What would Mr. Johnson make of that statement? Surely this is Jefferson as the American Lenin. Mr. Hitchens draws the comparison a little more tentatively: “Reviewed through the prism of historical perspective, this disconcerting ruthlessness reads a little like the manifestoes of later starry-eyed travelers who felt that ultimate history had been attained by revolutions in Russia, China or Cuba.”

Mr. Hitchens, hardly known for pulling his punches, is rather tender here, refracting his indictment through qualifying images and qualifications. After all, this is Thomas Jefferson, author of America – not only because his hand drew up the Declaration of Independence, but also because through the Louisiana Purchase he made his country a continental power.

Mr. Hitchens never gives Jefferson less than his due, but the biographer is determined not to sentimentalize his subject as preceding generations of biographers did, writing about Jefferson “as if he were not a male mammal at all.” There was plenty of circumstantial evidence to warrant the story of Jefferson’s sexual involvement with his slave, Sally Hemings, Mr. Hitchens notes. He enumerates the points in Annette Gordon-Reed’s book, published just before DNA evidence clinched her argument that the liaison had to be treated seriously.

Mr. Hitchens sets out to debunk not so much Thomas Jefferson as his biographers: “In the case of Dumas Malone, whose enormous hagiography of Jefferson has been ‘standard’ for far too long, one suspects that the historian had great difficulty considering the question of carnal knowledge at all.” If Mr. Hitchens sounds a tad like Gore Vidal, that is because Mr. Vidal is one of the biographer’s inspirations. “Burr” is surely one of Mr. Vidal’s finest works of fiction, and Mr. Hitchens is right to single out that novel’s vivid, eviscerating portrayal of Jefferson.

I only wish Mr. Hitchens had gone a step further and acknowledged Fawn Brodie, whose biography “Jefferson: An Intimate Biography” was attacked with scorn by her colleagues. To be sure, Brodie was speculating, and her narrative is suffused with perhapses and must-have-beens, but in her case such suppositional biography awakened an inquiry into both history and historiography that leads to Ms. Gordon-Reed and Mr. Hitchens.

If I have made Mr. Hitchens sound like only a faultfinder, I beg the reader’s pardon. In fact, the centerpiece of this biography is the biographer’s account of the Louisiana Purchase. Jefferson well knew that the Constitution gave him no authority to double the size of his country. He even contemplated, Mr. Hitchens points out, a constitutional amendment that would accommodate the acquisition of new territory. But Napoleon was having second thoughts about unloading his property, and Jefferson felt he had to act quickly.

This was much more than a land deal, Mr. Hitchens rightly insists. Purchasing the Louisiana territory was a great act of the imagination that Jefferson had been contemplating for decades. Without Jefferson there would have been no Lewis and Clark – only a belated acknowledgment of how vulnerable, without the movement west, America would have been, hemmed in by the French, Spanish, and British possessions in the New World.

Indeed, Thomas Jefferson the geopolitical thinker justifies Mr. Hitchens’s subtitle. Neither the biographer nor his subject observes the legal niceties; in some cases, the very notion of liberty requires extralegal measures. It is hard to see how Mr. Hitchens could advance this position without implicitly adopting the worldview that Mr. Johnson brashly announces at the outset. Here it is, then, that these masterful biographers shake hands.