domain of validity of information-driven interactions, and therefore of the concept of pragmatic information per se, is limited to the classical macroscopic domain. The reason is that, as we shall discuss extensively below, in the subatomic quantum domain spatial or temporal patterns cannot always be defined or identified in a univocal, stable or causal way. This in turn is related to fundamental and exclusive properties of quantum systems, which we shall examine now taking into account the definition of pragmatic information given in section 1.

Revisiting some relevant quantum facts
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For the purpose of exploring the role of pragmatic information in quantum mechanics it is opportune to present, in greatly simplified fashion, some experiment-based “quantum facts in a nutshell’’.[^11] To emphasize that the peculiar behavior of a quantum system is not the result of some mathematical properties of linear algebra and differential equations but, rather, representative of *physical* facts happening “out there”, we shall deliberately refrain from referring to abstract postulates, theorems and properties of Hilbert spaces with which most textbooks introduce the subject.

Given a *single* quantum system that has been physically prepared in a certain way, it is *impossible in principle* to determine or verify its particular 