Chapter One
Four Plates and One Cake
The first argument begins before the knife moves. There are four plates around the table, but five people may eat. One person is fetching tea and has not been counted. If you cut four equal pieces now, you can honestly say that every visible plate has the same amount. You cannot honestly say that everyone has been treated fairly. The size of the slices is only one part of the story. You must also know who belongs in the count.
That sounds obvious in a dining room. It becomes less obvious when the table is a schedule, a common fund or a place in a queue. The people who happen to be present can decide according to an impeccable rule. The rule might be applied without favour, and yet the person whose name was left off the list will still have reason to object. Before asking how to divide a good, ask what the good is, who has a claim to it, and who is made to carry any burden attached to it.
A cake is a convenient example because a slice has an edge. You can compare two pieces at a glance. Many things we argue about are less tidy. A volunteer team has an afternoon of free time, but some members must collect children before dusk. A family has a spare room, but the person who needs privacy most may not be the one who occupies the least space. A neighbourhood has a common garden, and one group wants flowers while another wants room for games. In each case, saying that everyone gets the same amount conceals a question about what counts as an amount.
