I see the expression of... economy clearly in the gradual reduction of the statical laws of machines to a single one, viz. , the principle of virtual… - Ernst Mach

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I see the expression of... economy clearly in the gradual reduction of the statical laws of machines to a single one, viz. , the principle of virtual work: in the replacement of Kepler's laws by Newton's single law... and in the [subsequent] reduction, simplification and clarification of the laws of dynamics. I see clearly the biological-economical adaptation of ideas, which takes place by the principles of continuity (permanence) and of adequate definition and splits the concept 'heat' into the two concepts of 'temperature' and 'quantity of heat'; and I see how the concept 'quantity of heat' leads on to 'latent heat', and to the concepts of 'energy' and 'entropy'.