The third assumption, and by far the most pernicious, is a behavioral model that describes human beings as something called "homo economicus," which basically means that we are all perfectly selfish, perfectly rational and relentlessly self-maximizing.
La tercera suposición, y hasta ahora la más perniciosa, es un modelo de comportamiento que describe a los seres humanos como algo llamado "Homo economicus", que básicamente significa que  todos somos perfectamente egoístas, perfectamente racionales e implacablemente auto-maximizadores.