In contrast to Piaget's genetic individualism, Vygotsky maintained that the development of higher mental functions is sociogenetic, arguing that any function in the child's cognitive development appears twice, first on the social plane and then on the psychological plane. The move from the social plane to the psychological is semiotically mediated; in fact, this semiotic mediation is the deep meaning of human social interaction. And since due to its inherent characteristics, language is the most pervasive modality for social interaction, it follows that language is also the most powerful tool for semiotic mediation. This theory of human cognitive development offers powerful insights into the relations between mind, language and society; however, its formulation does give rise to certain problems. The first part of this paper examines the two key concepts of higher mental function and semiotic mediation, drawing attention to some of the problems in Vygotsky's conceptualisation of the relation between the two. It is argued that being intimately related to social interaction, semiotic mediation is susceptible to variation, but the Vygotskian framework fails to assign a coherent place to such variation. Further, to accord a central place to verbal interaction in this sociogenetic process calls for some element in the theory which would account for the over-all nature and forms of social interaction, but no such theoretical apparatus is to be found in the Vygotskian framework. It has been suggested recently that these crucial problems in Vygotsky's framework might be resolved by appealing to Bakhtin's concept of speech genre-the more so since in Bakhtin's view of speech genre, heterglossia forms an integral element. Although at first glance this suggestion appears reasonable, a closer examination of Bakhtin's writing reveals that our optimism might be premature, that in fact there are features of Bakhtin's writing which make it almost impossible to use his notions in the analysis of speech genre-a concept very close to that of register in the systemic functional model. In drawing attention to these problems, the second part of the paper briefly compares Bernstein's views on the role of verbal interaction in the creation of variant forms of human consciousness. The paper concludes by a discussion of certain foundational issues in relating language, society and mental development.