The Sleepwalkers: A History of Man's Changing Vision of the Universe

The Sleepwalkers: A History of Man's Changing Vision of the Universe is a 1959 book by Arthur Koestler. It traces the history of Western cosmology from ancient Mesopotamia to Isaac Newton. He suggests that discoveries in science arise through a process akin to sleepwalking. Not that they arise by chance, but rather that scientists are neither fully aware of what guides their research, nor are they fully aware of the implications of what they discover.

A central theme of the book is the changing relationship between faith and reason. Koestler explores how these seemingly contradictory threads existed harmoniously in many of the greatest intellectuals of the West. He illustrates that while the two are estranged today, in the past the most ground-breaking thinkers were often very spiritual.

Another recurrent theme of this book is the breaking of paradigms in order to create new ones. People, scientists included, cling to cherished old beliefs with such love and attachment that they refuse to see what is wrong in their ideas and the truth in the new ideas that will replace them. (This point was developed a few years afterwards by Thomas Kuhn in "The Structure of Scientific Revolutions", in which the concept of "paradigm shift" came to the fore.)

Without denying the greatness of Galileo Galilei and the other modern scientists, he pointed out their mistakes and sometimes intellectual dishonesty, arguing that: "The scientific revolution's intellectual giants were dwarfs from a moral point of view". "The conclusion he puts forward at the end of the book is that modern science is trying too hard to be rational. Scientists have been at their best when they allowed themselves to behave as 'sleepwalkers,' instead of trying too earnestly to ratiocinate."