From [1]:
A man has arrived at the grocery store to go shopping, but realizes he’s forgotten his shopping list. Unbenknownst to him, a spy is following him tasked with writing a list of everything that is put into the grocery cart. There are now two lists of groceries that have dual relationships to what is put into the cart:
The original shopping list:
If we want to know whether an item that is put into the cart is ‘correct’, we must look to the shopping list
This list has authority over what is put into the cart: the list sets the standards of correctness.
The spy’s list:
This, conversely, says nothing about what should be put into the cart.
If we want to know whether something written on the list is ‘correct’, we must look to the shopping cart.
The cart has authority over the spy’s list.