The aim of this paper is to show an experiment of giving to mathematics’ topics (on geometric loci) ethical meanings, so that students can own the mathematical topic, seen as connected with their own lives, and can use mathematical reasoning to reflect on their own states of mind and feelings. The theoretical frameworks to design the activity are the Teaching for Robust Understanding Framework and the Mathem-Ethics methodology. Investigated students are teenagers. Analyses of students’ productions are briefly described at the end of the paper.