As I write, the world population is a little more than seven billion people. If we could see them all at once we would see a prodigious amount of activity, people engaged in building, walking, running, driving, buying, selling, planning, counting, watching, talking, listening, making love, eating, cleaning, carrying, and involved in the thousands of other actions in which people take part. And if you could observe a large number of individuals from afar, you would see that they are connecting ﬁ rst with this person and then with another. Humankind is a relentlessly active, ever-changing, ceaseless mass of billions of actions and interactions every second. We interact with others to accomplish things that we cannot realize by ourselves.