Like most critics of the molecular manufacturing concept, Jones is attacking a straw man. Yes, Drexler’s initial vision of how to design nano-scale machines was a bit naïve, but we’ve known that since the 1990s and no one is claiming otherwise. The fact that mechanical engineering at the nano scale is different than at the macro scale should surprise no one, but different does not mean impossible (or even more difficult, really). See, for example, the extensive work of Robert Freitas analyzing the actual challenges and opportunities of nano-scale medical engineering.