The Trifunctional Hypothesis is a controversial conjecture proposed by French mythographer Georges Dumézil. The hypothesis states that Indo-European religion has societies and religions divided into three similar roles: warriors, priests, and farmers.
The heart of the hypothesis is that both the society and the mythology are so divided. Each social group has its own god or family of gods to represent it, and that the function of both the group in its society and the function of the god or gods in the pantheon match. A recent alternate name for the hypothesis is function theory (not to be confused with the field within mathematics of the same name).
Dumézil believed that this tripartite division resulted in the arrangement of
Medieval feudal society (an historic example not noted by Dumézil) was divided into:
Dumézil argued that this dual sovereignty was expressed by pairs of gods such as
Alternatively the roles can be represented by quasi-historical hero-figures, such as
They can also be represented by distinct religious confraternities, such as the
Dumézil's trifunctional hypothesis has received a great deal of criticism, both before and since his death in 1986. Some commentators consider it as much a form of mythology as the myths which he studied. Others point out that the tripartite division may be more of an artifact of Dumézil's own way of understanding mythologies and societies rather than an organizing principle used in the societies themselves.
Critics of the tripartite system point out that there is no evidence that persons in these societies recognized an explicitly three-way division either of their gods or of their society, and that when there is written or mythological evidence, the caste or pantheon division is usually not three-way. For example the Norse gods were explicitly divided into two groups, the Aesir and the Vanir, not three; similarly, the caste system in India was(is) divided into four or five castes, again not three. If the critics are correct, then the trifunctional hypothesis would be an example of a selection effect.