During World War II there was a “shotgun wedding” forged in the processes of designing feedback mechanisms used to control gunfire targeting fast-moving enemy aircraft. Hendrik Bode perceived the shotgun marriage as a union of the classic regulator approach and long-distance telephone communications engineering. Norbert Weiner took the wedding description a step further by nesting communication engineering into a statistical mechanics framework in which the information engineer had to filter the useful signal from the useless noise. A main goal in designing weapon-fire control systems was to use negative feedback loops to ensure the stability of a system that was always in a transient mode. In the 1950s, control engineers such as Arnold Tustin, Bill Phillips, and Charles Holt offered their new analytic tools of block diagrams of systems with feedback loops, stability criteria, and physical analogues to model the economy, realize the promise of stability of employment and prices, and avoid another depression similar to that of the 1930s. By the early 1970s Paul Samuelson and the rational expectations theorists were primed to be receptive to a second, Cold War shotgun wedding in control engineering. Richard Bellman described it as a marriage of classical optimization theory and the probabilistic theory of stochastic processes.

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