My purpose in this paper is to show the evolution of the relationship between nonmonotonic logic and logic programming. I think that there are two periods in the evolution of this relationship. The first one isthe point of contact between these two fields that had been developed independently. In the second period, as I will show, the motivation to propose three-valued nonmonotonic logic comes from the study of the relationship between these two fields, and not from the study of nonmonotonic logic itself.

Pretendo usar o exemplo dos nomes de percursos de valores como prova de que, contrariamente ao que Michael Resnik e Michael Dummett sustentam, Frege nunca abandonou o seu princípio do contexto: “Apenas no contexto de uma sentenya tem uma palavra significado”. Em particular, pretendo mostrar que a prova da completude com relação ao significado, que Frege tentou introduzir na linguagem formal das Grundgesetze der Arithmetik, baseia-se em uma aplicação do principio do contexto, e que, em consequencia, tambem nomes de percursos de valores tem significado apenas nocontexto de uma sentença. A teoria Fregeana do sentido e do significado somente pode ser entendida adequadamente sob o pano de fundo do princfpio do contexto.Taking course-of-values names as an example, I want to show that, contrary to what Michael Resnik and Michael Dummett claim, Frege never abandoned his context principle “Only in the context of a sentence do words have meaning”. In particular, I want to show that Frege’s attempted proof of referentiality for the formal language of Grundgesetze der Arithmetik rests on the context principle and that, consequently, course-of-values names have a reference only in the context of a sentence. It is only in the light of the context principle that Frege’s theory of sense and reference can be understood appropriately.

La argumentación de Frege contra la definibilidad de la verdad pretende mostrar que una definición de verdad es circular o nos involucra en un regreso al infinito. En la obra de Frege cabe distinguir dos nociones de verdad: la verdad expresada mediante el termine “verdadero” y la verdad expresada mediante la aserción. La argumentación de Frege no muestra que el términe “verdadero” sea indefinible, pero, si se acepta la concepción de Frege acerca de la aserción, de su argumentación, adecuadamente reformulada, cabe concluir la indefinibilidad de la verdad en su segunda acepción.Frege’s argumentation against the definability of truth aims to show that a definition of truth is circular or involves us in an infinite regress. In Frege’s work two notions of truth can be distinguished: truth expressed by the word “true” and truth conveyed by the assertion. Frege’s argumentation does not show that the word “true” is undefinable, but, if Frege’s view on assertion is accepted, then from his argumentation, suitably reformulated, the undefinability of truth in the second sense can be concluded.