Pluralistic ignorance
Pluralistic ignorance can be contrasted with the false consensus effect. In pluralistic ignorance, people privately disdain but publicly support a norm (or a belief), while the false consensus effect causes people to wrongly assume that most people think like they do, while in reality most people do not think like they do (and express the disagreement openly). For instance, pluralistic ignorance may lead a student to drink alcohol excessively because she believes that everyone else does that, while in reality everyone else also wishes they could avoid binge drinking, but no one expresses that due to the fear of being ostracized. A false consensus for the same situation would mean that the student believes that most other people do not enjoy excessive drinking, while in fact most other people do enjoy that and openly express their opinion about it.
Value pluralism
Value-pluralism is a theory in metaethics, rather than a theory of normative ethics, or a set of values in itself. Oxford philosopher and historian of ideas Isaiah Berlin is credited with being the first to popularize a substantial work describing the theory of objective value-pluralism, bringing it to the attention of academia (cf. the Isaiah Berlin Virtual Library). The related idea that fundamental values can and, in some cases, do conflict with each other is prominent in the thought of Max Weber, captured in his notion of "polytheism".