During a class of the course on Philosophy and Rhetoric, a student expressed his views on the impossibility to settle many of our disagreements through dialogue.He would say that proof of this fact was the impossibility to convince a religious fanatic to stop using his body as an instrument to leap into terrorist action.The argument on the disagreements developed within a presentation of Walter Brice Gallie's thesis (1998) on "essentially contested concepts", also called "controversial concepts".According to this British philosopher, influenced by Wittgenstein's theses, traditional philosophy has unsuccessfully dealt with the issue of disagreement on the definitions of certain fundamental concepts.