I’m a Frog is another gem of a picture book by Mo Willems, published this year. It’s one of a series of books about best friends Piggie and Elephant Gerald. Willems’ books are clever and thoughtful, and frequently philosophically provocative.

In I’m a Frog, Piggie tells Gerald that she is a frog. Gerald perplexed, responds, “I was sure you were a pig. You look like a pig. And your name is Piggie.”

“I was a pig. Now I am a frog,” Piggie informs Gerald.

“When did you become a frog?” Gerald asks.

“About five minutes ago,” Piggie replies.

Gerald is beside himself.

Gerald begins to worry that he too might become a frog. Piggie reassures him by explaining that she is just pretending. “What is that?” Gerald wants to know.

“Pretending is when you act like something you are not.”

Gerald is fascinated by this news. “You can just do that?” he wonders.

Why is Gerald sure that Piggie can’t be a frog? He says that Piggie looks like a pig and her name is Piggie. Is this good evidence for concluding that Piggie is a pig and not a frog? How do we know something is a pig (or a frog, or a person)?

What does it mean to “pretend?” If we think we are something, does that make us this thing? Is what counts what other people think we are? What’s the difference between pretending and lying? Why do we pretend? Can we pretend to be anything we want?

Last year in a kindergarten class, when asked if there’s anything we can’t pretend to be, one student claimed, “You can’t pretend to be yourself, because you are yourself.”