This paper lays out theoretical considerations and first analyses on the giving of and asking for reasons among preschool children age 3–7 in natural child-child play interaction. It attempts to give an integrated, multimodal analysis of the verbal, paraverbal and extraverbal means of these reasoning activities. In the data it finds many instances of younger children who are giving reasons during play interaction. Often these reasoning activities do not occur in an open conflict and are not primarily directed at working out a local dissensus. Rather, these interactions seem to foreground the epistemic function of argumentation. The paper argues that these practices should be understood and researched as early forms of argumentation. Keywords: argumentation, validity, multimodality, child-child communication, cooperation