  Quantum mechanics forces us to reconsider certain aspects of classical
causality. The 'central mystery' of quantum mechanics manifests in different
ways, depending on the interpretation. This mystery can be formulated as the
possibility of selecting part of the initial conditions of the Universe
'retroactively'. This talk aims to show that there is a global, timeless,
'bird's view' of the spacetime, which makes this mystery more reasonable. We
will review some well-known quantum effects from the perspective of global
consistency.
