This paper aims at showing that the disconnection between formal structures and theoretical content in economic model building could lead to undesirable consequences. In this sense, linking formal and verbal contents by means of coherent and relevant interpretations is worth the effort. For it is a relatively simple way of helping to improve the usefulness of mathematical economic theorization. By way of illustration of these ideas, the paper discusses the interpretation which Arrow and Debreu

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... hemselves put on the inclusion of free goods in their proof of existence of a general equilibrium.