  Unitarity is a pillar of quantum theory. Nevertheless, it is also a source of
several of its conceptual problems. We note that in a world where measurements
are relational, as is the case in gravitation, quantum mechanics exhibits a
fundamental level of loss of coherence. This can be the key to solving, among
others, the puzzles posed by the black hole information paradox, the formation
of inhomogeneities in cosmology and the measurement problem in quantum
mechanics.
