Léon Festinger

Suppose an individual believes something with his whole heart; suppose further that he has a commitment to this belief, that he has taken irrevocable actions because of it; finally, suppose that he is presented with evidence, unequivocal and undeniable evidence, that his belief is wrong: what will happen? The individual will frequently emerge, not only unshaken, but even more convinced of the truth of his beliefs than ever before. Indeed, he may even show a new fervor about convincing and converting other people to his view.

L’homme de foi est inébranlable. Dites-lui votre désaccord, il vous tourne le dos. Montrez-lui des faits et des chiffres, il vous interroge sur leur provenance. Faites appel à la logique, il ne voit pas en quoi cela le concerne.