The aim of this article is to analyze and explain in more detail Waismann’s idea of the open texture of concept (Die Porosität der Begriffe) as a means for criticizing the principle of verifiability and to point out its distorted understanding as an open text. The open texture or porosity of a concept should relate to its potential, intensional indeterminacy – to signal the doubts that may arise in its application under unforeseen circumstances. Extensional essentialism is present in the background of this view. Against this view, Tichý presented his approach of intensional essentialism. On the basis of this approach we have enriched the critique of the open texture of concepts by the distinction between distinctive and scientific concepts and their correlations of various strengths. Furthermore, we have explained Waismann’s examples of a “giant cat” and “radioactive gold” as a replacement of one distinctive concept by another, both of them closely related in terms of their content, they have the same name and they are correlated with the same scientific concept with an unchanged essence.