  This paper offers a synthesis of the positions in the literature regarding
controversies about the multiverse. After reviewing some simple elements of
modern cosmology and its observational limitations, we will present the history
of the ideas that led, first, to the proposal of the anthropic principle and,
years later, to the possible existence of causally disconnected domains,
eventually endowed with their own laws and fundamental constants, not all
compatible with the existence of observers, which were globally baptized with
the confusing name of parallel universes or multiverse.
