„It [science] has as its highest principle and most coveted aim the solution of the problem to condense all natural phenomena which have been observed and are still to be observed into one simple principle, that allows the computation of past and more especially of future processes from present ones. …Amid the more or less general laws which mark the achievements of physical science during the course of the last centuries, the principle of least action is perhaps that which, as regards form and content, may claim to come nearest to that ideal final aim of theoretical research.“
— Max Planck German theoretical physicist 1858 - 1947
As quoted by Morris Kline, Mathematics and the Physical World (1959) Ch. 25: From Calculus to Cosmic Planning, pp. 441–42.