The French statesman Charles Maurice de Talleyrand, Duc de Talleyrand-Périgord (1754-1838), remains the classic case of a successful turncoat in politics. For half a century he served every French regime except that of the Revolutionary "Terror."

Charles Maurice de Talleyrand was a masterful diplomat of the old school as ambassador and foreign minister. Admired and often distrusted, sometimes even feared by those he served, he was not easily replaced as a negotiator of infinite wiles. Talleyrand has been an extraordinarily difficult figure for historians to understand and appraise. His moral corruption is beyond question: he was an unabashed liar and deceiver; he not only took but sought bribes from those with whom he was negotiating; and he lived with a niece as his mistress for decades. He repeatedly shifted political allegiance without visible compunction and possessed no political principle on which he would stand firm to...