In this city you can expect to go downtown and buy almost any food at any time. Yet, there's no planning authority for food or food distribution. Food deliveries are being made every day, nobody's planning how they get there. And it's easy enough to establish that if somehow, magically, delivery of food was stopped, there would be about a week or two of food on the shelves. Long before that, though, there'd be tremendous riots and fluctuations.
Nobody thinks or worries about it.
It's a great example of a complex adaptive system. Now, what if somebody decided, as they sometimes did in the seventeenth century, to build the ideal city. Let's play God. Well, that's hard. Now, adaptation gives you a clue.