Maupertuis proposed in 1744 the "principle of least action", applying it to the refraction of light. This paper discusses the foundation of Maupertuis' work and the criticism it received from d'Alembert and d'Arcy. This analysis shows that the principle of least action was not well grounded, since the reflection and refraction of light do not obey a general principle of minimum.293455463P.L.M. Maupertuis, Histoire de l'Académie Royale des Sciences, année M.DCCXLIV, avec les Mémoires de Mathématique et de Physique tirez des Registres de cette Académie, 417 (1748)Moreira, I.C., (1999) Revista Brasileira de Ensino de Física, 21, p. 172Newton, I., (1952) Mathematical Principles of Natural Philosophy, , Encyclopaedia Britannica, ChicagoJ.R. d'Al...