"The most important idea in the history of social analysis"

What's the one major thing that economics teaches?  I can hear the answer from the back of the room: from Jeffrey Tucker, who calls it "the most important idea in the history of social analysis" -- a "description of reality that is all around us but rarely noticed" -- one that has been around for many centuries,yet "first discovered by late-medieval monks working in Spain. It was given scientific precision in the classical period. It is the basis of advances in social theory in the 20th century. "

In fact [says Tucker, it is an essential part of the case for freedom. It was the basis of the belief of our ancestors that they could throw off tyrannical rule and still not have society descend into poverty and chaos. The failure to comprehend this idea is at the very root of the pervasive bias against liberty and free enterprise in our times, on the left and the right.

What's he talking about?  Go and see ...