  It is explained in detail why the Anthropic Principle (AP) cannot yield any
falsifiable predictions, and therefore cannot be a part of science. Cases which
have been claimed as successful predictions from the AP are shown to be not
that. Either they are uncontroversial applications of selection principles in
one universe (as in Dicke's argument), or the predictions made do not actually
logically depend on any assumption about life or intelligence, but instead
depend only on arguments from observed facts (as in the case of arguments by
Hoyle and Weinberg). The Principle of Mediocrity is also examined and shown to
be unreliable, as arguments for factually true conclusions can easily be
modified to lead to false conclusions by reasonable changes in the
specification of the ensemble in which we are assumed to be typical.
  We show however that it is still possible to make falsifiable predictions
from theories of multiverses, if the ensemble predicted has certain properties
specified here. An example of such a falsifiable multiverse theory is
cosmological natural selection. It is reviewed here and it is argued that the
theory remains unfalsified. But it is very vulnerable to falsification by
current observations, which shows that it is a scientific theory.
  The consequences for recent discussions of the AP in the context of string
theory are discussed.
