IPE Theories

Adam Smith once wrote that “It is not from the benevolence of the butcher, the brewer or the baker, that we expect our dinner, but from their regard to their own interest.”  This seemingly self-evident logic has helped propel economic liberalism as the dominant school of thought in the postwar period. 

Is economic liberalism (aka free market capitalism) the most efficient and productive economic model we have?  What about the alternative schools of thought?  Are they serious challengers?  Why or why not?