London, August 1854. Cholera swept through Soho, provoking more or less off the wall theories about what it was and how it spread. The medical establishment was highly sold on the commonsense "miasmic" theory — smells and drains and the like. People believed the key to conquering cholera was piping sewage away from people. It was, in a way, but... one result was engineering the sewage away from people, into the Thames, whose water they then drank. There’s everything right about modern sewerage, but putting it in without understanding Cholera meant spending millions inadvertently making its progress easier...
The heroes of Steven Johnson’s wonderful page turner are John Snow, Doctor, and the Revd Henry Whitehead, curate of St Luke’s. Both showed a willingness to think things through pragmaticlly rather than dogmatically to back up hypothesis with painstaking local research. Both showed great courage, especialy Whitehead in staying with the dying and survivors, trying to work out what was really going on. I remember noting as a research student the way in which young Anglo-Catholic clergy in 1866 won credibility for their cause by staying alongside the poor and dying when almost everybody else had fled during London’ last major cholera outbreak.
The parish system, for all its compromises and limitations from a suburban bourgeois point of view, worked by people of self-sacrificing faith, was socially transformational in Victorian London. Church works as dispersed reality, as well as, if not sometimes better than, the gathered righteous model. If you actually believe the gospel is about serving everyone, you can do a lot worse than parcel out a patch on a map and get stuck in.
Mr Johnson goes on to draw really interesting and challenging conclusions about our life and future. Cities could easily be the greenest, most fulfilling, most creative, artistic and efficient way for us to populate the planet — but they could also be the most vulnerable to disease or attack.
The disease bit is fascinating, especially in these days of heightened awareness around Swine flu. As it was 150 years ago, potty or inspired pet theories jostle with hard science to map out a sensible response. By and large, though, the book is confident our level of bioengineering undertstanding and technology is proceeding on a par with, or even faster than the threat. 
Unfortunately the same could not be said about the great non-bio fruit of twentieth century science and technology, the nuclear bomb. We may come to look back on the good ol’ Cold War of 1945-1990, balanced mutually assured destruction, as a golden age of innocence, unless we find a way get our heads and hearts around the moral and humanitarian dimension of these babies, brighter than a thousand suns.Turn that against a City, and the Ghost map will be very much more basic than Snow’s cholera map of 1854...
