Print the following twice, the second time in quotes.
"Print the following twice, the second time in quotes."

This idea was elaborated by von Neumann in the early 1950’s. Shortly afterward, two guys (I think their names were Crick and Watson) found a physical system that actually obeys these rules. You and I, along with all living things on Earth, are basically walking computer programs with the semantics:

Build a baby that acts on the following instructions, and also contains a copy of those instructions in its reproductive organs.
"Build a baby that acts on the following instructions, and also contains a copy of those instructions in its reproductive organs."