In the 1670s a Delft cloth merchant, Antonie van Leeuwenhoek, wrote to the Royal Society in London that a drop of water was full of tiny living animals. He wrote in plain Dutch, because he had no Latin, and he never told anyone how he made the little lenses he saw them through; that secret went with him. So nobody in London could simply check. What the Society did instead was ask for witnesses: a few respectable men of Delft, among them a minister of the English church there, went to his house, looked down his lens, and vouched for what they had seen. It is an odd way for a science to begin. The first report of a world too small for anyone to see was settled the way you settle a will: not by seeing it for yourself, but by finding people of good character who were in the room.