An ideology is a collection of ideas or beliefs shared by a group of people. It may be a connected set of ideas, or a style of thought, or a world-view. It was coined by a French philosopher, Destutt de Tracy in 1801/5.

There are two main types of ideologies: political ideologies, and epistemological ideologies. Political ideologies are sets of ethical ideas about how a country should be run. Epistemological ideologies are sets of ideas about the philosophy, the Universe, and how people should make decisions.