It’s pretty easy to see that a rock and a chipmunk are different. The rock doesn’t do much of anything except erode slowly. The chipmunk, on the other hand, is a flurry of activity. It endlessly scans its environment in search of food or danger. And when either one shows up, the chipmunk is quick to react. At a more fundamental level, however, what really is the difference between the inanimate rock and the very animate chipmunk? What’s the diff…