The theory of mediation (TDM) is a clinical anthropology that diffracts human reason into four planes of rationality and allows the deconstruction of cultural phenomena into the structures of the sign, the tool, the person and the norm. The deconstruction of the sacred through the lens of TDM shows that religion is similar to a language and that it is always related to a culture. The interrelation between culture and religion shows that religion differs along with societies, but also that religion can turn into ideology, like myths, especially as a reaction against the ideology of modernity. TDM can be used to dissociate fundamentalism from essentialism in term of aim, but also dissociate fundamentalism as ideology from fundamentalism as a personal discipline.