To find a substitute for laboratory experiments, economists pay close attention to the natural experiments offered by history.
Economics is the study of how society manages its scarce resources. In most societies, resources are allocated not by an all-powerful dictator but through the combined actions of millions of households and firms.
It is too early to say there is a consensus about how all these topics fit together. Yet one can say that the new classical challenge has been met: Keynesian economics has been reincarnated into a body with firm microeconomic muscle.