I was talking with my niece recently about the Earth’s shape. She had learned that the Earth is a sphere, and she asked me a question I wasn’t expecting: “Why, if the Earth is a circle, why is it always flat wherever we are?!?!”

What a beautiful question. Children question assumptions that adults accept without scrutiny. They don’t take things for granted the way we do – they want to understand why.

But children’s questions aren’t always this innocent and scientific. When I was in India, I found myself contemplating the much darker questions that poor children must ask about the stark class differences surrounding them. Questions like: “Why do we live in a tiny shed in their yard while they have such a large house?” or “Why can’t we eat together with them?”

These questions are heartbreaking because they’re so hard to answer. And I think that’s precisely the point. Moral issues often become painfully evident when examined through children’s innocent curiosity. If something cannot be reasonably defended to a questioning child, it likely represents a moral flaw in our society.

Think about slavery. Segregation. Contemporary issues in policing. Marriage equality. In each case, try explaining the injustice to a child asking “why?” – you’ll find it nearly impossible to justify.

Children’s questions matter. They cut through the rationalizations we’ve built up over years of socialization. I hope I never forget their importance when it comes to examining fundamental fairness in our society.