In micro-economic theory of general equilibrium, there is no immeasurability. But an economical agent is not only the subject of this kind of rationality. He is not only a homo economicus. His activity is also, as Paul Samuelson pointed out, "future oriented". This means that he had to put together rational measurability with the immeasurability of an open, unknown future. Because of this ongoing play of measurability and immeasurability, too many options are open. Only choices and institutions can stabilize—for the time being—society.