'Rules Rather than Discretion: The Inconsistency of Optimal Plans' (pdf) by Finn E Kydland and Edward E Prescott, Journal of Political Economy 1977:

“Optimal control theory is an appropriate planning device for situations in which current outcomes and movements of the system's state depend only on current and past policy decisions and on the current state. Current decisions of economics agents depend in part on their expectations of future policy actions. Only if these expectations were invariant to the future policy plan selected would optimal control theory be appropriate.”

Niccolo Machiavelli, The Prince, 1532

“The promise given was a necessity of the past; the word broken is a necessity of the present.”