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Sleepwalking amid new ideas

Book Book Review, Title The Sleepwalkers, Author Arthur Koestler, Rating 4.0, Sleepwalking amid new ideas

The Sleepwalkers

Arthur Koestler

Book Review

Arthur Koestler's book Sleepwalkers: A History of Man's Changing Vision of the Universe is an ambitious attempt to describe the development of Western cosmology and astronomy from the Greeks to Newton, with particular focus on Copernicus, Brahe, Kepler, and Galileo. Koestler did not see science as a linear and unbroken line of rational progression; instead he viewed the course of the history of ideas as somnambulant: Many ideas were stumbled upon by men with goals and mindsets alien to the very ideas they uncovered.

Arthur Koestler was a lesser known, but nonetheless brilliant, 20th century literary phenomenon, at ease equally with politics, philosophy, literature and science, and his breadth informs this capable history of early modern cosmology. His account emphasizes the intellectual confusion that necessarily accompanies new ideas. As Koestler describes it, these cosmologists of the 16th and 17th centuries did not fully recognize what they had found, or valued their discoveries for mystical or mistaken reasons, or were unable to provide reasonable evidence for their new ideas, while often behaving more dogmatically than the skeptical religious or scholastic audiences of their times.


Johannes Kepler. PD-US.


Kepler’s three great planetary laws, upon which Newton built his modern synthesis of the workings of the solar system, were published many years apart, and generally buried in a complex geometrical model that made no sense then, and certainly doesn’t now. Kepler explained the motion of the heavens with highly mystical mathematical and geometrical models in the tradition of Pythagoras. Yet Kepler was quite influential in his latter days because his mathematical models were more accurate than the prevailing Aristotelian (Ptolemaic) methods, and produced more accurate astronomical tables needed by navigators and astronomers. It might be said that Kepler made little effort to understand the underlying physics, but even that is not really true; Kepler posited a sort of quasi-force acting centrally to explain the elliptical paths he had painstakingly observed in the more precise observations he inherited from Tycho Brahe, a ‘force’ not unlike the gravitational force finally posited by Newton. He just wasn’t quite there, and he certainly was unable to communicate clearly to those around him the most important elements of his new approach, or why it clearly supported the heliocentric model of the solar system.


Galileo Galilei, 1636, by Sustermans. PD-US.


The author’s treatment of Galileo’s interactions with the Catholic Church trods some new and interesting ground. Koestler provides an excellent summary of Galileo’s controversy with the Church. It is commonly asserted that Galileo’s trial by the Inquisition for heresy was triggered by his insistence on a Sun-centered Copernican model of the solar system over the established and Church-approved earth-centered Aristotelian cosmological model, which the Church endorsed because they thought it was in alignment with the teachings of the Bible. In fact his inquisitorial moments were precipitated by his publishing of a Dialogue, or formal disputation, on the merits of both systems, in which he did not openly espouse either system. But in publishing this Dialogue, he raised the hackles of the established Church, because first, he published it in Italian, rather than Latin, opening the argument beyond churchmen and scholars (practically the same thing at the time), who had been debating these ideas vigorously, only behind the scenes, as was the custom (similarly, Luther’s battle with the Church began not when he published his 95 theses against Papal excesses, but when he published them in German and disseminated them via the printing press).

Second, although he did not openly espouse the Copernican system in his Dialogue, he clearly and heavily favored them; he was already on probation with the Church, so to speak, having been formally warned not to favor Copernican cosmology in print some years earlier. Third, he made the principal advocate for Aristotelian cosmology in his Dialogues a veritable idiot, even to the point of calling him Simplicio! Fourth, he all but quoted the then sitting Pope, and then mocked the Pope’s ideas; this was probably the last straw for the Pope, who had been, prior to that, a strong advocate of Galileo, and was thereupon the one who called Galileo to the Inquisition. This story, although not typically told in textbooks, is generally agreed upon by historians of science.

-CC BY-SA 3.0, Sailko

Ptolemaic planetary model. Note the many gears within gears.. Attrib: Sailko, CC BY-SA 3.0. Click to view enlarged picture


What Koestler adds is that Galileo’s arguments concerning the superiority of the Copernican system were false on their merits! He suggests that Galileo’s defense of the Copernican system by arguing that the the tides were formed by the earth’s rotational movements around the Sun and on its own axis was not compelling in his time (and subsequently proved fallacious). He also suggests that Galileo had completely ignored Kepler’s various communications to him, and at that time Kepler was the only person in the world who understood the key to explaining the motions of the planets around the Sun: They traveled in slightly elliptical orbits rather than circular ones called for by Copernicus. It is quite possible that he ignored Kepler’s correspondence because Kepler buried the elliptical model in his mystical geometrical explanations.

Without that vital understanding of elliptical orbits, the Copernican system was little more than a shift of the center of the planetary motions from the earth to the Sun, and otherwise based on the same mechanical approach which Ptolemy used (circular orbits, circles on circles, or epicycles, and the shifting of circles slightly off-center, or deferents) and was in fact no simpler and only slightly more accurate than the prevailing Ptolemaic system. In addition, Galileo, in fact, had not fully mastered the Ptolemaic or Copernican models, as had some of the Aristotelian scholars whom he mocked, who were able to effectively argue that he had no real proofs as to the superiority of the Copernican system over the Ptolemaic system, and in fact had just baldly (and in modern parlance, unscientifically) asserted it!

The author suggests that, while the Catholic Church has many sins for which they are responsible, in the case of Galileo they did not suppress good science for the sake of dogma; in fact, Koestler argues that Galileo could be construed as more dogmatic! Nor did the Church treat him as extremely as they had many others, but gave him an out, and allowed him live his life out under house arrest; during these last years he was allowed to publish other important scientific work, including his most influential thinking on forces and motion

Book Briefly Noted, Title The Ascent Of Man, Author J. Bronowski, Rating 4.0,

The Ascent Of Man

J. Bronowski

Briefly Noted

Jacob Bronowski provides another emphasis, in his Ascent of Man, pointing out that the Church’s use of the Inquisition to censor Galileo had a severe dampening effect on science in Catholic-controlled Europe, moving scientific leadership effectively to the North, where it flourished for two hundred years under Protestant-controlled territories.

(This account makes Galileo look unlike the great scientist that he most certainly was. Galileo, if you accept this interpretation of events, was foolish and proud in this instance, but he was also the founder of modern dynamics, the study and understanding of forces, and a most formidable intellect, one who’s place in the pantheon of great scientists is unquestioned. It may be instructive to look at a modern example of the same thing: Linus Pauling won a Nobel Prize for his sweeping mastery of quantum mechanical chemical bonding, yet later in his life was an enthusiastic proponent of taking mass amounts of vitamin C to ward off cancer, without, of course, any science to back up his claims.)

I would highly recommend this book to those interested in the history of science, and in the nature of the propagation of scientific ideas.

A gift from my Jenn and Benn.

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