This week I’ve been reading Carlo Rovelli’s new book, On the Equality of All Things. Rovelli, a theoretical physicist, is one of science’s great communicators. He argues that philosophers and others need to rethink what they mean by reality.
Many of us hold a view that’s close to the 17th-century philosopher John Locke’s. If I look at someone wearing a red raincoat, the coat really exists, and has some so-called primary qualities (solidity, shape, dimensions), but the redness that I perceive is a secondary quality that arises from the interaction of the primary qualities of the coat with my perceptual system. The redness isn’t intrinsic to the “real” coat but is rather something that arises when a human being with a particular range of sensory perceptors and brain processes perceives the coat.
There are obviously individual differences, and some will see that red coat as orange. The primary qualities of the object are there, though, and real, regardless of how anyone perceives the coat. They don’t change.
According to Rovelli, this is all wrong, but not enough people have noticed yet. To him, the idea of an objective reality “out there” unobserved is outmoded. It just doesn’t make sense to talk about properties or things existing independently of a perspective on them.
Quantum mechanics, the mind-boggling way of understanding the world that emerged at the beginning of the 20th century and which physicists are constantly debating, changes everything. I don’t pretend to understand it – and take some consolation from Nobel laureate physicist Richard Feynman’s comment that “nobody really understands quantum mechanics”.
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He didn’t mean that even physicists don’t understand how to use it: they are really good at that. It allows them to make accurate predictions about all kinds of phenomena. It’s rather that quantum mechanics is a black box even to physicists. They understand that it works, but not precisely why.
The weirdness of quantum mechanics is exemplified by quantum superposition. Particles can sometimes act like waves. Observation changes their state.
Before observation, the state of a system is indeterminate. It doesn’t make sense to ask where a particle is until it is observed. This is bizarre, as Erwin Schrõdinger’s thought experiment about a cat was intended to show – he thought it led to absurdity.
For Rovelli, an important consequence of his relational interpretation of quantum mechanics is that it explodes the idea of an objective reality lurking out there unobserved, a view that many philosophers still hold. It might be a useful way of thinking about the world we inhabit day-to-day, but it isn’t accurate. Far from it. Reality is always relational, a series of intertwined processes. It’s perspectival, never independent. Every description of the world is contextual. There is no ultimate view of things, no God’s-eye view of an objective reality.
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One of the delights of reading Rovelli’s book is that he is such a good writer he gives the mathematically challenged the feeling of understanding how things are and a sense of why physicists believe what they do, and some of the implications of that, without using formulae. He is also superb at conveying the strangeness of the world that physics has revealed. But we non-physicists must take his particular perspective on quantum mechanics on trust.
Physics is hard to assess if you can’t follow the complex mathematics underpinning it and which justifies the theories. Most of us inevitably rely on trustworthy popularisers such as Carl Sagan, Feynman, Stephen Hawking, and Rovelli. In this, physics differs from a great deal of philosophy. With philosophy, non-philosophers can follow and, most importantly, judge at least some of the most important justificatory reasoning if it is well explained and jargon-free, particularly in areas such as practical ethics.
Not so with relativity and quantum mechanics. There, non-physicists must forever remain enthusiastic spectators rather than players.
