In my talk I shall discuss the content and consequences of the transparency principle (TP) according to which one each occasion when someone uses something as a sign of something else the vehicle of the signs becomes transparent to the consciousness of the user of the sign.(TP) has been introduced by Edmund Husserl in his Logical Investigations and then studied by Polish semioticians (Stanisław Ossowski, Leon Koj). In particular, Leon Koj (Koj (1979)) proposed an axiomatic account of the principle and argued that it provides a solution to semantic antinomies (like the liar or Grelling paradox).In my talk I would like to discuss the rationale behind Koj's opinion (and compare Koj's solution with others know replies to semantic paradoxes), additionally I shall discuss also the relations of the transparency principle to other transparency principles discussed in the contemporary philosophy of language and mind. In particular, I shall attempt to connect the principle to the possible solution to the problem of indexical dynamics: the question if (and to what extent) failure of knowing the actual context of use might result either in contentless thought or in the thought that has a content inaccessible to the subject.Koj, L. (1979). The Principle of Transparency and Semantic Antinomies. In: Pelc, J. (eds) Semiotics in Poland 1984–1969. Synthese Library, vol 119. Springer, Dordrecht.