In 1946 Henry Hazlitt wrote a famous little book called Economics in one Lesson. In the seventh paragraph of the first chapter he stated the lesson in one single sentence: "The art of economics consists of not merely looking at the immediate but at the longer effects of any act or policy; it consists in tracing the consequence of that policy not merely for one group but all groups."
The following twenty-two chapters were simply examples of that one lesson.
In part three of this little book which Hazlitt titled, "The Lesson Restated", he reiterated that single sentence lesson: "Economics as we have now seen again and again is a science of recognizing secondary consequences. It is also a science of seeing general consequences. It is the science of tracing the effects of some proposed or existing policy not only on some special interest in the short run, but on the general interest in the long run."
The matter of the Crary sign has been an outstanding illustration of that simple lesson.