The paper includes reflections on statements (formulated in the Polish language) containing the expression of the so-called double negation (e.g. 'Nieprawda, ze nie bylem wczoraj w kinie' (Eng. It is not true that I wasn't at the cinema yesterday). It highlights certain interpretation problems arising when applying rules of formal logic to the analysis of structures of the kind. From the point of view of logic, a sentence based on double negation is semantically equal to an affirmative one, and thus, in a natural language, it is redundant. The authoress questions the formal perspective and proves the usefulness of double negation in everyday discourse, basing her conclusions on observations of how the expressions under consideration are used in the context of communication and referring to the analyses conducted in A. Boguslawski's work (2003).