Interaction or intersubjectivity? A reply to Lerman

Lerman, in his challenge to radical constructivism, presented Vygotsky as a n irreconcilable opponent to Piaget's genetic epistemology and thus to von Glasersfeld's radical constructivism. We argue that Lerman's stance does no t reflect mon Glasersfeld's opinion of Vygotsky's work, nor does it reflect Vygotsky's opinion of Piaget's work. We question Lerman's interpretation o f radical constructivism and explain how the ideas of interaction, intersub jectivity, and social goals make sense in it. We then establish compatibili ty between the analytic units in Vygotsky's and mon Glasersfeld's models an d contrast them with Lerman's analytic unit. Consequently, we question Lerm an's interpretation of Vygotsky. Finally, we question Lerman's use of Vygot sky's work in mathematics education, and we contrast that use with how we u se mon Glasersfeld's radical constructivism.