Sir

Your Editorial article “Nanotech is not so scary” (Nature 421, 299; 2003) attributes to me the idea of building devices that replicate “by manipulating atoms one at a time”, and points out that several leading figures in nanotechnology research argue that this is unfeasible. As well they might. My proposal is, and has always been (see Proc. Natl Acad. Sci. USA 78, 5275–5278; 1981), to build atomically precise structures by using molecular machinery to direct conventional chemical reaction events with subnanometre positional control.

If this is fundamentally unfeasible, then so is life. Thus, these critics are mistaking atomic precision for atom-by-atom manipulation, while failing to address the actual concepts analysed in the technical literature. These misdirected arguments have needlessly confused the discussion of genuine long-term safety concerns.