The mechnosynthesis fans at places like the Centre for Irresponisble Promotion of Unfeasble Nanotechnologies always get a bit hot under the collar when criticised, and the first line of attack is always to quote Lord Kelvin’s famous 1882 remark that “Heavier than air flying machines are impossible.”
I am not convinced that this is a valid argument when looking at molecular nanotechnology as we have had almost twenty years of proponents saying that some kind of Utopian singularity is just around the corner – surely this would be also worth quoting as an example of a failed prediction?
Kelvin based his opinion on prevailing scientific opinion at the time, whereas the Drexlerians ignore scientific opinion in the same way that advocates of intelligent design and creationism ignore the evidence of the fossil record. That probably explains why they are given short shrift by the mainstream scientific community, and resort to dismissing two and half thousand years of science for the sake of a bunch of beliefs backed up with no evidence.
Perhaps this is a job for renowned sceptic and arch debunker Richard Dawkins?