How do you know
That the earth is round
That cats have four legs
That we're on solid ground?

How can you know
That time will fly by
That everything grows old
That some things will die?

How can you tell
That your family's awake
That nature's alive
It's a risk that you take
To tell the whole world that you know what you know
And you can't tell how smart someone is,
Until you ask: How do you know?