A lot of our thinking, and even our perception, has to do not only with what is, but what might be, and what would have been. That is, the imagination is an important part of our intellectual life. And learning to use our imaginations without losing sight of reality is part of growing up. What is the imagination, and what led Mother Nature to make it such an important part of our make-up? John and Ken discuss the imagination with Alison Gopnik, a leading scholar in the field of children’s learning.