by Terry Pratchett, Ian Stewart & Jack Cohen

Ebury Press


336pp/£18.99/April 2013

The Science of Discworld IV: Judgement Day

Reviewed by Steven H Silver

More than any of its predecessors, The Science of Discworld IV: Judgement Day, appears to have an axe to grind as Terry Pratchett, Ian Stewart and Jack Cohen return to explaining how our universe is set up by using Pratchett's Discworld as a background. Since the series began in 1999, a rise of religious literalists has obstructed scientific research and Messers Pratchett, Stewart, and Cohen do not pull their punches in ridiculing those extremists and explaining how science works.

Almost as much as the science the authors detail, The Science of Discworld IV: Judgement Day is about how science works.  While religious literalists see the explanation for natural phenomenon as rigid and unchanging, Stewart and Cohen are very clear about the fact that science must change as new evidence becomes apparent, something the literalists see as a weakness.  In fact, Stewart and Cohen are almost gleeful in pointing out that while they described the "Theia" theory of lunar origins in The Science of Discworld, the two men are "no longer convinced."1 They use this lack of conviction to discuss how scientific theory changes and what the current status of lunar origin is.

Scientific theory is something else the two are very clear about.  Often the detractors of science refer to theory without understanding what it means in a scientific context. Stewart and Cohen explain what that context is, ending by stating "Anyone who tries to convince you that evolution is 'only a theory' is confusing the second use with the first, either through intention to mislead or ignorance."2 The authors have similar harsh language for those who deny climate change and others who put religion or political expedience ahead of an honest understanding of science.

Understanding science is what the Science of Discworld series is about and the authors do their best to point out that scientific literacy is not a mystical revelation, but rather something that anyone can achieve if they read with an open mind.  Throughout the series, they have presented theories and explanations with a limited amount of technical jargon (some, of course, is necessary) and without resorting to throwing equations and diagrams at the reader.  Instead, they make science accessible by talking about the individuals who have made discoveries and formulated theories.

Stewart and Cohenís scientific explanations, however, are only part of the book. Just as in the previous volumes, Terry Pratchett provides a novella about the Wizards of Unseen University and their poking and prodding at the strange Roundworld which they created in the first volume.  This time, Pratchett's tells of a young librarian who has been sucked into Discworld from Roundworld and becomes embroiled in a dispute between the Wizards who created Roundworld and Reverend Stackpole of the Church of the Latter-Day Omnians, a sect who have rejected the teachings of the prophet Brutha.3 The Omnians are clearly a stand-in for the more literal and anti-science branches of religion.  Much of Pratchett's story is less than memorable, although it does build up to Pratchett's own version of Tennessee v. John Thomas Scopes.

3.See the events detailed in Small Gods, 1992.

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