A group of men want to measure the objects around them. They use similar measuring rods, and try to find out which objects are the same length as them. This is what happens: one man places his rod against the object to be measured; another does the same, but also sets up a microscope with which to view the ends of rod and object; a third man glances at his rod in his hands, and then at the object some distance from him; a fourth puts down his rod after looking at it carefully, and then goes to look at each object in turn; and lastly, one man takes his rod and bends it to fit whatever he is measuring. When the men report their findings, there is disagreement among them. Some say of a particular object that it is the same length as their rods, others that it is not. And we may suppose as well that no two of the men agree on the results for all the objects measured.