The preceding essay is a conflation of two articles: "Problems and Changes in the Empiricist Criterion of Meaning", Revue Internationale de Philosophie, No. 11 (1950), and "The Concept of Cognitive Significance: A Reconsideration", Proceedings of the American Academy of Arts and Sciences 80 (1951). In combining the two, I omitted particularly some parts of the first particle, which had been largely superseded by the second one;¹ I also made a few minor changes in the remaining text. Some of the general problems raised in the combined essay are pursued further in Aspects of Scientific Explanation, especially in "The Theoretician's Dilemma". In this Postscript, I propose simply to note some second thoughts concerning particular poits in the preceding essay.