What I found fascinating is that Matthews' delusions mirror very closely modern paranoid belief systems, mapped onto the primitive technology at the beginnings of the Industrial Revolution. James says that the Jacobins control his mind using a "pneumatic loom", which beams thoughts into his head using "mesmeric rays". Nowadays, victims (victims of something) say CIA agents and aliens control their minds using radio waves from sinister UFO machinery. Or, as the Wired piece shows, via the Web.
"Haslam's Key" suggested that these schizophrenic influences were also at large in writers of science fiction, who often appropriate modern technology in similar ways: that sf was as much of a product of physiological effects as the elaborate but consistent fantasies of those suffering from mental illness. I thought it was fun to paint the strange consistency of SF plots and habits onto the behavioural basins of mental disorder. It was rubbish, by the way. I'm pleased to find the guys around Area 51 have a much more intriguing hypothesis. They say that James Tilley Matthews was the first subject of a Benjamin Franklin/Anton Mesmer/Adam Weishaupt mind control device - that's still in use today. Ewige Blumenkraft!
(Haslam's Key, by the way, was particularly gruesome piece of tech invented by John Haslam around the same time as he was transcribing Matthews' complaints. It was a form of flattened spoon that could used to prise open patients' mouths for feeding them against their will. It's clear from the introduction to "Illustrations of Madness" that Haslam's aim in documenting Matthews was to confirm his madness to aristocrats who'd received convincingly sane letters from him pleading for release. Haslam achieves this, largely, by taking the piss.