David Bohm

David Bohm (Wilkes-Barre, Pennsylvania, 1917 – London, 1992) was a theoretical physicist whose work ranged across quantum theory, the philosophy of science and neuropsychology. He is widely regarded as one of the most original physicists of the twentieth century, and his ideas about the nature of reality and mind are still debated both inside and outside physics.

He was raised mainly by his father, who ran a furniture store and helped the local rabbi. Bohm became an agnostic as a teenager. He studied at Pennsylvania State College and then at Berkeley, where he earned his doctorate under Robert Oppenheimer. During the Second World War he was denied security clearance for the Manhattan Project, partly because of his left-wing politics, so he finished his thesis without access to some of his own research, which had been classified.

After the war he became an assistant professor at Princeton and worked with Einstein. During the McCarthy years he was called before a congressional committee, refused to give evidence against colleagues, and was suspended by the university. A request to move to Manchester was not granted, and at the invitation of Jayme Tiomno he took up a post in São Paulo in 1951. There he pursued a causal interpretation of quantum mechanics, first set out in his textbook Quantum Theory and then developed in papers from 1952. This line of work, known as the De Broglie–Bohm theory or pilot-wave theory, proposes non-local hidden variables yet makes predictions that match standard quantum mechanics. His analysis of the EPR argument also helped inspire John Bell's inequality. Earlier, at Berkeley, he had studied plasma behaviour, and a plasma effect now bears his name.

In 1955 he moved to Israel, and in 1957 to the University of Bristol. With Yakir Aharonov he described in 1959 the Aharonov–Bohm effect, in which a magnetic field affects a charged particle even when it travels through regions where the field is zero. In 1961 he became professor of theoretical physics at Birkbeck College, London.

His thinking went well beyond physics. Drawing on holography, he proposed a distinction between the implicate order, an underlying unity in which everything is enfolded, and the explicate order, the world of separate and apparently distinct things. He called the movement between them holomovement. With neuroscientist Karl Pribram he developed the holonomic model of the brain, in which memory and perception are spread across neural activity somewhat like a hologram. The model remains speculative and is not widely accepted in neuroscience. He also held a long series of dialogues with Jiddu Krishnamurti, published in several books, and argued that genuine dialogue could help heal social divisions.

After retiring in 1987 he continued his work on quantum theory with Basil Hiley. His final book, The Undivided Universe, appeared posthumously in 1993. In 1990 he was elected a Fellow of the Royal Society. His legacy lies in the foundations of physics, where his interpretation remains a standard reference point, in the philosophy of mind, and in the dialogue movements that take his ideas as a model for collective thinking.