A Revolution in Thought? How hemisphere theory helps us understand the metacrisis It is often remarked that though it may seem that we face numerous global crises of different kinds – environmental, social, political, cultural, economic, psychological, and so on – these crises are interrelated. The term ‘metacrisis’ has been invented to describe this predicament. However these crises are not merely adventitiously interrelated because each has an impact on and reinforces each of the others – though that may be true – but because they share roots at a deeper level in a way of thinking about ourselves and the world. What are these roots? Hemisphere theory, deeply grounded as it is in Darwinism and subsequent neuroscientific research, shows us that a new, far more complex, and more nuanced, appraisal of the bipartite brain – the product of the last 30 years of research – brings new insights into the human condition. There are vitally important clues to the understanding of human cognition and motivation embodied in the structure of the brain. These clues help explain why certain apparently unrelated phenomena tend to occur together, why outcomes that appear paradoxical are in reality predictable, and why many attempts to remedy them will prove inadequate since they are tackling only the manifestations of a problem that we need to address at its root – both in the psyche of the individual and that of a civilisation viewed as a whole. ‘Know thyself’ commanded the Delphian oracle: we need urgently to learn to do so, and this synergy of philosophy and neuroscience appears to offer the most promising way. Dr Iain McGilchrist is a Quondam Fellow of All Souls College, Oxford, an Associate Fellow of Green Templeton College, Oxford, a Fellow of the Royal College of Psychiatrists, a Fellow of the Royal Society of Arts, and former Consultant Psychiatrist and Clinical Director at the Bethlem Royal & Maudsley Hospital, London. He has been a Research Fellow in neuroimaging at Johns Hopkins Hospital, Baltimore and a Fellow of the Institute of Advanced Studies in Stellenbosch. He has published original articles and research papers in a wide range of publications on topics in literature, philosophy, medicine and psychiatry. He is the author of a number of books, but is best-known for The Master and his Emissary: The Divided Brain and the Making of the Western World (Yale 2009); and his book on neuroscience, epistemology and ontology, The Matter with Things: Our Brains, Our Delusions and the Unmaking of the World (Perspectiva 2021).