I’ve read a lot of popular science books over the years, but never until now have I felt a real urge to go and learn the maths I’d need to properly understand the work. I feel as though, if I had read this book twenty, or even ten years ago, I might have done just that – changed direction altogether and gone off to ferret around in obscure corners of the quantum. Of course, it is a different me that has read this book now, in 2019, and I would probably have responded differently a decade ago – Spawn has focussed her educational career in science, and my slavish devotion to reading New Scientist, for example, has only arisen as a consequence of us taking out a subscription for her. However, there is something I find unfeasibly exciting about investigating the fundamental principles that make the universe what it is. Smolin’s book, which is ‘popular’ science only inasmuch as it eschews any mathematics, looks at attempts to model the fundamental structure of matter and spacetime, and posits a new theoretical framework from which both quantum and relativistic behaviours could be derived.

This is not A Brief History of Time for quantum mechanics. Einstein’s Unfinished Revolution is a demanding text, a work of philosophical discourse as much as it is an exposition of science for the layperson. Smolin has made it his business to investigate philosophy, as an integral aspect of his attempts to imagine an approach to physics which can encompass the contradictory and counterintuitive results of modern theoretical and experimental work. Questions about quantum physics are questions about knowledge, information and subjectivity as much as they are questions about the physical universe – uncertainty means nothing without a thinking subject to experience it. This is, for Smolin, a fundamental shortcoming of quantum mechanics as a theorisation of the smallest scales of physics. For him, a theory should describe the universe as it would be in our absence, unobserved: he is a realist, not as the term is used in everyday discourse, but someone who believes fundamentally in the Real. The universe, for Smolin, is independent of us and of the ways our cognition frames it; he believes, furthermore, that human beings can and will develop a way to describe it as such.

Belief is an interesting word. The things that we believe are things that we hold to be true, irrespective of how we have arrived at that position. Smolin believes, clearly, in the predictive accuracy of certain theories and formulae, and he believes this because he has confirmed it for himself, or because scientists he has no reason to doubt have confirmed it. But other things he believes because he has a powerful feeling that they must be true. For example, there is no empirical reason that necessitates a human capacity to understand the universe. There are many organisms on earth that are incapable of understanding even Newtonian physics, let alone the quantum, and the possibility is real that our cognitive capacities are not equal to the complexities of the Real. The Real is another matter of belief; of course logic suggests that there must be some physical substrate that pre-exists our propensity for naming and conceptualising the contents of our perceptual compass, but we can never see past the tools that are at our disposal for sensing and thinking about things. Again, we must take this on faith. It seems unlikely that Smolin harbours any theistic inclinations, but his faith in the Real and in its explainability are not irreligious. These are the articles that anchor his peregrinations through an intellectual landscape apparently devoid of any fixity.

I do not begrudge him this. In fact, I would argue that faith of some sort is essential to any functional sense of self. At some point we must decide to defer any lingering doubts we have about the existence of ourselves and the universe, and for the most part people do not actively doubt these things. Smolin talks about this near the end of the book: theorists like him have, at some point, to take a leap of faith in deciding what area they will work on, without any real way of knowing which avenue is likely to yield results. He has decided to pursue a realist interpretation of physics. This is, however, incompatible with the dominant versions of quantum mechanics.

The orthodoxy, within the dominant Copenhagen interpretation at least, has been to hold that the capacity of quantum mechanics to predict experimental results is not a sign of any particular fidelity to the structures it purports to describe, and even that there is no other reality subtending what’s observable. I am sympathetic with Smolin’s view that this discloses unfinished business, and that it should be a priority in physics to re-theorise fundamental physical structures in a way that does posit a complete and falsifiable account of what happens in detail at the smallest scales. However, his determined quest for a theory that allows us to peer through the fog of symbols and ideas to the actual Real seems quixotic. However precisely we can model the behaviour of particles, we will still speak and think about them using words and thoughts: even the complex and sophisticated technical language of physics will always be language, not the thing itself. And whenever we classify the world, breaking off a piece of it to say ‘here is a particular object’, that object, defined by properties or boundaries that we have assigned it, is always a product of our discourse.

The details of Smolin’s account of the various versions of quantum physics, and their relations to the question of realism, is too complex for me to have retained in detail, and certainly too wide-ranging to recapitulate it here. He examines a variety of approaches which meet his criteria for realism, several of which are very long-established, and have the capacity to generate the same predictions as quantum mechanics, whose dominance he ascribes largely to social causes, the power of orthodoxy and institutional inertia. These include the many-worlds interpretation, which Smolin characterises as ‘magical realism’, and the pilot wave theory, the first hidden-variable theory in quantum physics – a theory which introduces unobservable hypothetical entities. These are the early forebears of Smolin’s current efforts. Albert Einstein was the most prominent of the physicists present at the discovery of the quantum to remain convinced of the incompleteness of the theories developed to account for it, and his unsuccessful attempts to complete it constituted by far the greater part of his life’s work. This gives Smolin’s book its title, although Einstein’s work on the quantum plays relatively little part in his account.

Smolin moves on from a history of realist approaches to the quantum, to the work that he himself is engaged in. He has looked to philosophy for ways to re-conceptualise the search for a fundamental physical theory, and one of the most interesting things that I learned from his book is the importance of the role played by philosophers of physics, particularly a group working at Oxford University. His central insight seems to be that it requires a return to first principles to find a basis for unifying scientists’ seemingly incompatible understandings of the physical universe. His search for a theoretical structure that does not assume a fixed background, in other words one which gives rise to all the characteristics of the observable universe, has led him to some remarkable places.

To do justice to these lines of thought, even the philosophical ones which I am more able to grasp, is far beyond the scope of this journal entry. Suffice it to say that Smolin begins with a philosophical understanding of what is required for a valid theoretical framework, and works from there to produce an appropriate physical theory. His efforts revolve around modelling the causal relations between events, in a way which can explain the emergence of space (a relatively un-real structure, as he tells it), time (fundamental and very real), and the troubling quantum phenomenon of non-locality (explained as manifesting a more fundamental form of proximity than that which appears in three-dimensional space, which also arises from the same fundamental structures). These ideas demand a great deal of the reader’s close attention, if the book is to make any sense to them. If they give it that attention, it will levy a further set of imaginative demands, asking them to engage with a sense of the Real which is likely to be deeply unfamiliar. For myself, such an engagement is a rarely paralleled reward for the simple act of reading a book. If you need to ask yourself whether that unfamiliarity justifies the effort of reading and understanding, this may not be the book for you; but for me the opportunity to fundamentally question the structure of reality, with a guide of Smolin’s considerable erudition, is unmissable.