History does not repeat itself, although sometimes echoes of the past seem remarkably familiar to us. Each event in history is, however, unique, just as every person is. Generally speaking, though, we humans (including historians like me) do not hesitate to wonder if history is repeating itself: we ponder whether the recession will be another Great Depression, Afghanistan is another Vietnam, the 2012 presidential election will be another 1996, Obama is another Jimmy Carter, Obama is another Bill Clinton, and, my favorite, whether Obama is another Lincoln (case in point: Garry Wills' essay on Obama's Tucson speech in the latest New York Review of Books). Maybe what we mean, or what we think we mean, is that there is sometimes a resemblance between the past and present, something a bit more reminiscent than just a vague feeling, as we all get every once in a while, of déjà vu. When those similarities strike us, we wonder if history is repeating itself, for good or ill.