The secular state, as an ideal paradigm, is a conquest of the enlightenment. Nowadays, its most dangerous enemy is considered to be fundamentalism. It has become common to understand the notion of fundamentalism as a multiplicity of movements united by the main goal of restoring some form of confessional state. The author proposes a redefinition of fundamentalism as the outcome of the synthesis of three factors, each of them also redefined in specialized meanings: fanaticism, integralism, totalitarianism. In this sense, fundamentalism is built upon an inseparable bond between auctoritas and veritas; and, as such, opposed to the secular state, founded on the separation between sovereignty and truth. To confront fundamentalism, a secular state must promote critical and plural public education, as the school for the formation of free thought. In the age of obtuse power, however, this is difficult to happen.