This paper argues that intersubjectivity cannot be grounded in individual mental or representational content. Intersubjectivity, therefore, is not equivalent to “common knowledge”, rather common knowledge (indeed individual knowledge in the true representational sense) depends upon intersubjectivity. Intersubjectivity is the fundamental basis of what Durkheim (and Searle following him) have called “social facts”, which are irreducible to (though they depend upon) biological and individual psychological facts. Intersubjectivity is based upon participation in joint action, and such participation also implicates the shared material, interobjective world. Participatory engagement with signifying objects accompanies and underpins the child’s entry into the symbolic realm of language, and makes possible the development of subjectivity and cultural identity through participation in narrative practices.