In Fact, Fiction and Forecast, Nelson Goodman claims that the problem of justifying induction is not something over and above the problem of describing valid induction. Such claim seems to open up the possibility that the new riddle of induction could be addressed empirically. Discoveries about psychological preferences for projecting certain classes of objects could function as a criterion for determining which predicates are after all projectible. In this paper, I argue that Goodman's claim must be construed within his project for constructional definitions, which is methodologically oriented by reflective equilibrium. The description of inductive practice is committed to the articulation of the extension of the class selected by the predicate ‘valid induction’. The mutual adjustment between theoretical considerations and inductive practice involved in the proposal of a definition of ‘valid induction’ must preserve that practice as much as possible, there is no way to get rid of entrenchment. Empirical discoveries about the psychological mechanism that underlies projections may help that adjustment but they cannot substitute the role played by the entrenchment of predicates.

Versão a convite de um artigo homônimo para o italiano.

In 1995 the publication of Marleen Rozemond’s paper Descartes’s Case for Dualism has triggered the revival of the discussion on his argument in favor of the real distinction between body and soul among the Anglo-Saxon scholars. In particular the discussion then resumed was on the necessity of introducing a hidden premise (the so called the attribute premise) in order to regain its probatory character. This debate has reflected on the Cartesian studies in Brazil and my objective in this text is to bring to the debate two texts still unexplored related to this interpretative problem. My hypothesis is that the attempts to justify the thesis that the substance has exactly one principal attribute have not yet better succeeded because they underestimated the contribution brought about by the transformation of the notion of nature entailed by the introduction of the concept of principal attribute. Understanding the Cartesian proof of substantial dualism, and more particularly the “attribute premise”, would involve, I suggest, the thesis according to which the concept of principal attribute, insofar as it expresses the essence of the substance, is not – and cannot be – according to Descartes, an abstract universal, but rather a particular nature