Actually, as a system, the economy itself is not explainable by any one person or theory.  It's really very complex, but complexity is merely defined as being comprised of many identical or similar parts, each operating on the same few basic principals (ie. it is composed of people who, though different, operate on largely the same principals, like "buy low, sell high" or "hold onto a stock as long as possible" or even just on the principal of trying to profit).  Despite this, it's devilishly hard to understand how and why the economy functions how it does once you get to the scale of the US economy or even the world economy.  There are so many variables, so many people and transactions and motives and it goes on... 

Many people have many theories, but the economy doesn't seem to pay them much mind.