“If everything that exists has a place, place too will have a place, and so on ad infinitum.” — Aristotle. It’s not very often that the author of a book discussing economics and sociology for a general readership starts with a quote by the Greek philosopher Aristotle. But when the writer is the thought-provoking intellectual Richard Florida — who claims in his new book, “Who’s Your City?,” that the selection of where to live ranks as life’s most important decision — it’s easier to see why he found Aristotle’s quote both appropriate and prescient.