Planting the Voluntaryist Seed

A short conversation between my 6-year-old son and I before reading our bedtime story went as follows:
Son: Dad, what is that second word on your book in the bathroom?
Dad: "Defined", the title is "Liberty Defined" (Ron Paul).
Son: What is liberty?
Dad: Liberty is when nobody else is trying to control you.
Son: Do we have liberty here (where we live, America)?
Dad: We have a significant amount of liberty in America, but we are still controlled in many ways.
Son: Who controls us?
Dad: The government controls us in many ways, bad guys sometimes try to control us.
Son: Oh.