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Quantum Reality - Jim Baggott ****

At one time it was popular amongst some physicists to be extremely critical of philosophy. For example, in their book The Grand Design, Stephen Hawking and Leonard Mlodinow aimed to answer a series of what have long been seen as philosophical (such as 'Why are we here?', 'What is the nature of reality?' and 'Did the universe need a creator?') by ignoring philosophy and taking a purely scientific viewpoint. Philosophy, those authors assured us, like religion, was now dead.

I'm afraid Hawking and Mlodinow failed to convince, which is why it's perfectly reasonable for Jim Baggott to come up with a book on a physics topic, what 'lies beneath' quantum theory, and, along the way, to spend a fair amount of the book introducing philosophical concepts put across by philosophers.

Quantum physics is arguably unique amongst the hard sciences in having a range of interpretations that run from 'We don't know what is happening and never will' (typified in the response 'Shut up and calculate') all the way through to detailed interpretations which do away with some of the problems we face in the traditional approach, at the cost of introducing a whole new series of problems, such as the extravagant requirement for the 'many worlds' interpretation that there are vast numbers of parallel universes.

Baggott is a master of taking complex concepts and making them surprisingly accessible. For much of what's difficult and confusing about quantum physics interpretations he succeeds in doing this admirably. For example, he gives the first explanation I've ever read of one of the more philosophical interpretations of quantum theory, quantum Bayesianism, or QBism, which I found in the slightest bit comprehensible. For me, the book was worth reading for that alone.

I also found that Baggott gave fascinating details on the philosophical side I was unaware of, from the philosophers of science like Karl Popper to the hardcore philosophers behind some of the concepts required to understand quantum interpretations, such as Immanuel Kant. Personally, I've never been hugely bothered about philosophy, but it is simply impossible to really dig into these interpretations without taking philosophy on board, so this was great.

What I thought was a little less accessible was the descriptions of quantum phenomena. These were illustrated with little pictograms which I found hard to follow, particularly as the print was so small I couldn't read the text. Sometimes, in the effort to avoid getting too technical - for example in describing what was meant by an operator and an expectation value - there was insufficient detail to get your head around the concept. And I did find a metaphor repeatedly used involving an island of metaphysical reality, the sea of representation, the ship of science and the land of empirical reality (with Scylla and Charybdis thrown in, which I can't really remember what they were intended to be) more confusing than helpful. But these are small details that didn't prevent the book being fascinating.

Throughout, Baggott is approachable and often has a wonderful turn of phrase (I loved, for example, the description of Paul Feyerabend as 'a Loki among philosophers of science'). In the end, a lot of the tension in the book is between realist interpretations ('There is something underneath that we could in principle uncover') and anti-realist ('It is impossible to ever discover a reality beneath - shut up and calculate'). As someone who feels more comfortable in the anti-realist camp, I couldn't agree with Baggott's assessment that realist interpretations are 'more palatable' - I think it's useful to read Philip Ball's Beyond Weird as well for a contrast - but I very much enjoyed getting a better background on the different possibilities.

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Review by Brian Clegg

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