In this Comment, we elaborate upon Mulkay's discussion of the rhetorics of hope and fear in the UK debate over research on human embryos, by focusing on the narrative strategies and cultural presuppositions that allow certain technological developments to be (re)presented as `hopeful' or `fearsome'. We argue that boundary talk and its associated vocabularies of purity and pollution provide Mulkay's rhetorics with a semantic construction kit. They are the means through which `hope' and `fear', as rhetorical effects, are achieved. Finally, we discuss the wider significance that could be attributed to these discursive moves - that is, as pointers to how the relationship of a culture to its technologies is constituted.