The Anthropic Principle Revisited

Abstract

The usage of the anthropic principle in modern cosmology is reviewed. It is argued that its recent use to explain the observedvalues of cosmological parameters as most probable values for an ensemble of universes, is not justified. However, the anthropic principle can be invoked to argue that a vast number of universes must exist, in which the cosmological parameters and constants of nature take on different values. This argument lends support to the hypothesis of eternal inflation and suggests that at least some of the parameters of the Standard Model cannot be quantitatively derived from an underlying theory.