nomena (Duhem 1987, 86). In these lines, a distinction is made between essence and phenomena.14 This distinction is the basis for distinguishing between science and metaphysics. The essences are conceived as causes of the phenomena. The intelligence of man, on the one hand, know directly the phenomena and the laws according which these phenomena are related and, on the other hand, known indirectly something of the essences because the knowledge of the effects allows us to know something about the substances that produce these effects; however, this knowledge is neither complete nor adequate for these substances (Duhem 1987, 86). The distinction between essences and phenomena has led us to the distinction of two types of knowledge: the knowledge that human intelligence has of the phenomena and their laws, on the one hand, and, on the 11 In section X of chapter VI of the second part, section entitled "Le bon sens est juge des hypothèses qui doivent être abandonnées", also shows the reasons why the bon sens is the judge on the choice of the hypothesis. 12 Duhem does not seem to respond to the accusation of Abel Rey on "Mais nous n'avons eu ici que l'intention d'examiner la philosophie scientifique de M. Duhem, et non l'oeuvre scientifique elle-même" (Rey 1904, 743-744, emphasis added), as its defense goes to show that your "physical system" is positive and does not depend on the metaphysics or religion. However, the assertion of Rey that Duhem makes metaphysics can justify the response of the latter. 13 "A moins de borner la science à n'être qu'un recueil de recettes empiriques – et encore cette prétention n'est-elle pas le résultat plus ou moins conscient d'une tendance métaphysique? – les problèmes métaphysiques sont, à certains moments, si près des grandes questions scientifiques, l'esprit humain est si désireux de prolonger sa curiosité, en imaginant toujours de nouveaux pourquoi, qu'il est chimérique et abstrait de vouloir mettre un fossé infranchissable, et surtout infranchi entre la scien