“As we can not give a general definition of energy, the principle of the conservation of energy signifies simply that there is something which remains constant.”

— Henri Poincaré, book The Value of Science

Comme nous ne pouvons pas donner de l'énergie une définition générale, le principe de la conservation de l'énergie signifie simplement qu'il y a quelque chose qui demeure constant.
Source: The Value of Science (1905), Ch. 10: Is Science artificial?

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French mathematician, physicist, engineer, and philosopher … 1854–1912

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