Exclusivism
Exclusivism is the practice of being exclusive; mentality characterized by the disregard for opinions and ideas other than one's own, or the practice of organizing entities into groups by excluding those entities which possess certain traits. (for an opposite example, see essentialism).
Religious exclusivism
Religious exclusivism asserts that one religion is true and that all others are in error.
It has two forms:
Absolute exclusivism asserts that one must be born into the religion to be a true adherent. Historical examples are the religion of Athens during the golden age
Relative exclusivism asserts that conversion is mandatory. Christianity and Islam are some such examples. Cf Extra Ecclesiam Nulla Salus.
In Ancient Greece
The Decree of Diopithes (430 BCE) forbade the worship of and belief in gods other than those of the Olympian pantheon recognised by the Athenian polis. The introduction of other gods was treated as asebeia, or impiety, and was punishable by death. The philosophers Anaxagoras, Protagoras, Socrates, Stilpo, Theodorus of Cyrene, Aristotle, and Theophrastus were accused of impiety under this decree. Socrates was found guilty of the charge of introducing new gods and condemned to death by drinking hemlock.