In 2009, British psychiatrist Iain McGilchrist published “The Master and His Emissary: The Divided Brain and the Making of the Western World.” This 608-page work examines the specialized functions of the brain's two hemispheres. Its central idea is that the hemispheres do not simply differ in whether they are “logical” or “creative,” but attend to the world in fundamentally different ways: the left focuses on detail, while the right perceives the whole. In the title, the right hemisphere is the “master” and the left is the “emissary.” According to the author, these two worldviews have shaped Western civilization since the time of the ancient Greek philosopher Plato, and their growing conflict has implications for how the modern world is changing.
McGilchrist cites two main influences on his work. From psychiatrist John Cutting, he says, he learned that the difference between the hemispheres lies not in what they do, but in how they do it. From psychologist David McNeill, he adopted the idea that thought originates in the right hemisphere, is processed by the left for expression in language, and then its meaning is reintegrated by the right, which alone understands the overall meaning of a complex utterance.
In the book's introduction, the author notes that “there is, literally, a world of difference between the hemispheres.” Understanding exactly what this means, he explains, required a journey through many seemingly unrelated fields: not only neurology and psychology, but also philosophy, literature, the arts and, to some extent, archaeology and anthropology.
In the first part, titled “The Divided Brain,” McGilchrist replaces the popular, superficial view that one hemisphere is logical and the other creative. Instead, he describes two modes of attention that develop into very different hemispheric “personalities.” According to the book, the right hemisphere has a more direct relationship with physical bodies—our own and those of others—and with external reality as presented by the senses. This relationship makes it a mediator, the first and last stop for every experience.
In the second part, “How the Brain Has Shaped Our World,” the author describes the development of Western civilization as influenced by the functioning of the hemispheres. The journey begins in the ancient world, passes through the Renaissance and the Reformation, the Enlightenment, Romanticism and the Industrial Revolution, and reaches the modern and postmodern world. McGilchrist argues that today's civilization is increasingly dominated by the left hemisphere, to our detriment.
Some critics saw this argument as a warning that we are thinking increasingly like machines and risk losing what makes us human. Others, however, felt that the book went far beyond the neurological evidence.
Reception was mixed: philosopher Mary Midgley wrote in the Guardian that the book raises new questions and is “remarkably thought-provoking,” while neurologist Adam Zeman described it as a vast, absorbing and debatable thesis. Philosopher A. C. Grayling, meanwhile, praised the writing and scholarship but noted that neuroscience findings were not detailed enough to support the book's sweeping cultural conclusions.
The Economist described generalizations of “enormous scope” and argued that the book's second part had become detached from brain science. Psychologist Michael Corballis added that, although the work had been widely acclaimed, it went beyond the neurological evidence. Owen Flanagan challenged many aspects of the book and rejected it, saying that neither hemispheric differences nor the patterns of 2,500 years of Western history were well understood.
McGilchrist responded sharply, describing the criticism as superficial and misleading.
Despite the objections, the book was shortlisted for the Bristol Festival of Ideas book prize in 2010 and longlisted for the Royal Society science book prize that same year. It also inspired the documentary “The Divided Brain,” which the author himself endorsed.
Its subject connects with broader discussions about the philosophy of mind and theories such as Julian Jaynes's bicameral mind, while McGilchrist later returned with “The Matter with Things” in 2021.
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