This article is based on a semantics of the concepts implied in the pedagogical domain of marginality in order to highlight the central importance, from an ontological point of view, of difference. According to this perspective,the encounter with difference sets in motion the process of construction, organization and modification of knowled-ge. This idea has to do with the multiplicity of experiences and cognitive styles. By understanding within ourselves the plurality of which we are made up we create a space for the multiplicity to be, which leads to the understan-dingof the other, of what is different. The concept of difference leads us to its epistemical connotations, to the multidisciplinary story of crossbreeding which becomes a starting point for the reflexion about education. In the same way, the problem of margins forces us to become aware of the social shifts of the so-called applied ethics.