It's wrong to steal something from a friend.
John is extremely hungry.
John needs to find some food to eat.
John asks Reuben is he has any food to spare.
John decides to take some of Reuben's lunch off his desk without asking, and he eats it.
Reuben offers to share his bag of chips and John eats and is satisfied.
Reuben sees John eating his lunch and doesn't want to be friends anymore.