Pluralistic ignorance
In social psychology, pluralistic ignorance is a situation in which a majority of group members privately reject a norm, but go along with it because they incorrectly assume that most others accept it. This is also described as "no one believes, but everyone thinks that everyone believes". In short, pluralistic ignorance is a bias about a social group, held by the members of that social group.
Theology of religions
Pluralism is basically the belief that the world religions are true and equally valid in their communication of the truth about God, the world, and salvation. The chief expounder of this view is John Hick of Claremont Graduate School in California, who first propounded it in his book "God and the Universe of Faiths (1973)". It has been notably criticized in the declaration Dominus Iesus by Cardinal Joseph Ratzinger.