  I begin by examining the question of the quantum limits of knowledge by
briefly presenting the constraints of the theory that derive from its
mathematical structure (in particular the no-go theorems formulated by von
Neumann and Kochen and Specker). I then argue that these theorems reflect on a
formal level those practical and experimental settings that are needed to come
to know the properties of physical systems. In particular, I discuss some
aspects of this relationist and contextualist conception of reality by
comparing, in their apparent diversity, Bohr holistic and Rovelli relationist
interpretation of the formalism, that deep down share a unifying metaphysics of
dispositions and propensities. Both interpretations are based on the widely
shared fact that quantum mechanics does not describe previously definite
quantities. In the final part I show that, as a consequence of a relationist
and perspectival approach to quantum mechanics, the quantum state of the
universe regarded as an isolated system cannot be known in principle, so that
the universe must be described from within by dividing it into two arbitrary
parts. This is in fact the only way in which any two systems can exchange
information by being physically correlated.
