The Last Slice — How does "I cut, you choose" work, and how do you split something fairly?

The fairest way to split something between two people is to let one person cut and the other person pick first. The cutter's best move is then dead even, because whatever they make bigger is exactly what gets taken off them - so nobody has to be nice for it to come out fair. Sit at a kitchen table, get robbed of the big piece, take the knife, and find the only cut a greedy brother cannot beat. Then try it on a bag of five whole things that will not divide evenly. This is the rule the countries of the world used in 1982 to divide up the floor of the ocean.