Another Leo Lionni book, little blue and little yellow tells the story of two friends, both blobs of color, who love playing together, and one day hug each other so much that they both become green. Their parents declare that they are no longer who they were.

Like all the Lionni books I’ve been reading, this story has great philosophical energy. It makes me think about identity and what it is that makes us who we are – once little blue and little yellow are green, are they no longer blue and yellow? They still feel inside like blue and yellow. Can something change and still remain the same? If you change, are you still the same person? The story also raises questions about knowledge and belief: the parents are sure that little blue and little yellow are no longer themselves, but they base this belief solely on the way the children appear to them. Is that a good basis for believing something? Often things aren’t the way they look to us – and yet we persist in thinking we know things because we have seen them. When is appearance a reasonable basis for believing or knowing something?