  The logic--linguistic structure of quantum physics is analysed. The role of
formal systems and interpretations in the representation of nature is
investigated. The problems of decidability, completeness, and consistency can
affect quantum physics in different ways. Bohr's complementarity is of great
interest,because it is a contradictory proposition. We shall see that the
flowing of time prevents the birth of contradictions in nature, because it
makes a cut between two different, but complementary aspects of the reality.
