Towards the end of his second term as President, Thomas Jefferson received a letter from his granddaughter, who mentioned that she had been reading from the works of the Roman historian Tacitus. In his reply, Jefferson wrote: “Tacitus I consider the first writer in the world without a single exception. His book is a compound of history and morality of which we have no other example.” Given that Jefferson was extraordinarily well-read, one cannot help but wonder what he found so compelling. I would suggest that in order to understand Jefferson’s unique claims for Tacitus we need to consider two questions from Jefferson’s perspective: What is the historian’s role in a democratic republic? and Does Tacitus fulfill that role?