THE STRUCTURE OF DEMONIC REVOLUTIONS:

"Bedeviled: A Shadow History of Demons in Science" (Princeton University Press) is not a survey of Baal, Stolas, Volac, and their kin. Instead, Canales has gathered together in one book demons with very different origins and responsibilities--among them the scientist James Clerk Maxwell's demon, the physicist David Bohm's demon, the philosopher John Searle's demon, and the naturalist Charles Darwin's demon. These demons came into being at some of the world's leading universities and were promulgated in the pages of Science and Nature. They are not supernatural creatures; rather, they are particular kinds of thought experiments, placeholders of sorts for laws or theories or concepts not yet understood. Like the demon Jesus met, though, these are legion; at the very same time that science was said to be demystifying the world, Canales shows us, scientists were populating it all over again with the demonic.

According to Canales, a faculty member at the University of Illinois at Urbana-Champaign, modern demonology began with René Descartes, who imagined a demon into being in his "Meditations on First Philosophy," from 1641. The French philosopher was positing a thought experiment most often described today as the brain in a vat: however, instead of wondering if he was just a disembodied brain experiencing a simulated reality, Descartes proposed that "some malicious demon of the utmost power and cunning has employed all his energies in order to deceive me." Said demon could alter our senses and convince us of falsehoods, so that what we see, hear, or feel might not be real. Because anything might be a deception, we must assume everything is, and only through extreme skepticism can we distinguish the real from the unreal.

Descartes's demon was not immediately followed by others, but, in 1773, the French mathematician Pierre-Simon Laplace proposed a thought experiment of his own. He imagined a mysterious entity "who, for a given instant, embraces all the relationships of the beings of this universe." With that single instant of complete knowledge, Laplace wrote in an article on calculus, this entity "could determine for any time taken in the past or in the future the respective position, the movements, and generally the attachments of all these beings." Because Laplace's demon knew the present location of every single thing in the universe and all the forces acting on them, it could infer everything that had already happened and everything that would happen in the future.

Several decades before, John Locke had posited that, other than God, only angels and spirits might have such total knowledge. But Laplace argued that the universe was stable and predictable--this was why Edmond Halley could determine the regular arrival of a comet--and that, as a result, mathematical analysis could help us understand the universe in its entirety. It was therefore perfectly reasonable, even for those of us who don't possess infinite information and limitless cognitive power, to use what information we do have and what cognition we can summon to make sense of the world. Laplace's faith in scientific determinism helped inspire the creation of machines that could do the kinds of computations he attributed to his demon. Charles Babbage read Laplace's work, and cited it in accounts of his "Difference Engine" and "Analytical Engine," machines designed to perform calculations; Babbage's friend Ada Lovelace, who was tutored by Laplace's English translator, grasped the implications of Babbage's engines, and encouraged him to find additional applications for what are now considered some of the earliest computers.

Darwin knew Babbage, too, and talk of demons and determinism might well have helped shape his account of evolution. Darwin's notes on the subject originally included "a being infinitely more sagacious than man," one "with penetration sufficient to perceive differences in the outer and innermost organization quite imperceptible to man, and with forethought extending over future centuries to watch with unerring care and select for any object the offspring of an organism produced under the foregoing circumstances." 

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