Biotechnology, like Janus, faces both ways. On the one hand it is the industrialization of life; on the other, it is the greenest of technologies. Both these ideas, with their incompatible attendent political implications, have become subsumed in the single concept ‘biotechnology’. This duality has deep historical and linguistic roots, an examination of which can help in understanding both the multiplicity of definitions and the confusion of purposes that abound in biotechnology.