Constitution allows coordination and assurance

Picture yourself as one member of a large, genuinely diverse group — people of different religions (Hindu, Muslim, Christian, and some with no religion at all), different professions, different abilities, different tastes, different levels of wealth, different ages. Such a group is bound to disagree about almost everything: how much property a person should be allowed to own, whether schooling should be compulsory or left to parents, how much the group should spend on security versus, say, public parks, whether the group may ever discriminate against some of its own members. Every one of these questions will draw a different answer from different people. And yet, for all their disagreement, the members of this group still depend on each other and need to cooperate to live together at all.

What actually lets such a diverse group live together peacefully is not agreement on every question, but agreement on some basic rules — rules that are publicly known to everyone and are genuinely enforceable, not just written down and ignored. Publicity matters because a rule nobody knows about cannot coordinate anyone's behaviour. Enforceability matters even more: if people have no assurance that others will actually be made to follow the rules, they have no real reason to follow the rules themselves either. Saying that a rule is legally enforceable is precisely what gives everyone the confidence that others will comply, because breaking the rule carries a real consequence. …