In ethics, value pluralism (also known as ethical pluralism or moral pluralism) is the idea that there are several values which may be equally correct and fundamental, and yet in conflict with each other. In addition, value-pluralism postulates that in many cases, such incompatible values may be incommensurable, in the sense that there is no objective ordering of them in terms of importance. Value pluralism is opposed to value monism, which states that all other forms of value can be commensured with or reduced to a single form.
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".
