"It's all in Plato, all in Plato: Bless me, what do they teach them at these schools?"
―Digory Kirke[src]

Plato was a philosopher who lived on Earth, in classical Greece, who suggested the idea that worlds such as Earth were only copies of another, more real, version of that world.

Digory Kirke later discovered this to be true when he and the other Seven Friends of Narnia found that Aslan's Country was the real version of Earth, Narnia and other worlds.

He also made a minor joke about how children should have been taught better about Plato's work in schools.