This paper focuses on arguing and reasoning processes occurring at dinnertime family conversations. Its goal is to highlight the interplay between two sides of argumentative practices: the justification as social need to provide evidences for an assertion; the dialogic function of argumentation that refers to the goals arguers want to achieve during discussions. Through the analysis of a case study, the paper discusses a sequence in which a child resists his father’s directive by an elaborated argumentative strategy in order to achieve his goal. Results show how participants engage in opposing the other’s standpoint and are socialized to argumentative dialogues.