Ha-Joon Chang

A lot of things that we cannot buy and sell in markets used to be totally legal objects of market exchange - human beings when we had slavery, child labour, human organs, and so on. So there is no economic theory that actually says that you shouldn't have slavery or child labour because all these are political, ethical judgments.

Contrary to what professional economists will typically tell you, economics is not a science. All economic theories have underlying political and ethical assumptions, which make it impossible to prove them right or wrong in the way we can with theories in physics or chemistry.