Given the undeniable importance of entropy to the economic process, and the resulting fact that ‘sustainable economic growth’ is an oxymoron, how do we explain the unwavering devotion to continuous economic growth by economists, policy makers, and the general public in the face of ecological and natural resource limits? Apparently, people believe that the economic system faces no limits to growth or that the limits are far off. The laws of thermodynamics ensure that there are limits to growth. Now we must briefly address the question of how close those limits are.