Sounds like a bubble. But it wasn't, asserts Thompson, who is working on a history of bubbles. Tulip-bulb investors were neither mad nor delusional in 1636 and 1637. Rather, he says, they were rationally responding, in finest efficient-market fashion, to overlooked changes in the rules of tulip investing. [Slate, thanks to Ben]A very interesting and fact-based argument that the tulip craze, usually considered to be the world's most ignoble predecessor to the dotcom bubble, was not a bubble at all but a completely rational economic response.