On the Equality of All Things: Physics and Philosophy Carlo Rovelli Allen Lane (2026)

Physicist Carlo Rovelli has spent much of his career working on the theory of quantum gravity, which seeks to reconcile quantum mechanics with the general theory of relativity. But, as he explores in his latest book, On the Equality of All Things, he is increasingly pondering an even bigger question: whether there is an ultimate description of reality at all.

You used to think physics could offer an account of reality. What changed?

I think physics is a fabulous enterprise, but the world is more complicated than just a fundamental equation. It is genuinely complex, which means that understanding the basic rules doesn’t tell us much about understanding the phenomena that we are interested in.

In the book, I say that fundamental physics is overrated. High-energy physics, particle physics, quantum gravity — it’s great science. I love it. It’s fantastic. It tells us something about the world. But stop thinking that it is the root of everything else.

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Why shouldn’t we think like that?

My work is on quantum gravity, trying to write a theory that describes gravitational phenomena for which quantum theory cannot be disregarded. I find it super interesting because it pushes us to rethink reality. But I think it is a mistake to see physics as getting to the ultimate reality. The question of whether there is an ultimate reality is a bad question. ‘Ultimate’ doesn’t mean anything. Generality doesn’t mean better understanding.

I go running in the morning, and I try to run faster and faster. I have an objective to run faster, but that does not mean I want to reach the speed of light. In the same way, I want to know more about the world, but the very idea of knowing the ultimate reality seems an illusion and part of a world view that I think we should drop.

Do you think the field of physics suffers from hubris?

Yes, I think it does. I don’t think it is a particularly serious sin, but it has created problems for physics. Physicists have oversold the field, sometimes with good motivation. I think about theoretical physicist Stephen Hawking saying “philosophy is dead now”. This has created a colossal push against science, which I think is bad. People say: “Come on, you scientists pretended to be the arbiters of reality. You’re not.”

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Why does that matter?

I think a lot of the physics literature is wasted, as well as some experimental efforts. Look how much experimental effort has been put into checking theories that then didn’t work. The most striking example has been supersymmetry (which predicts a partner particle for each of the basic building blocks of matter). How could the entire community be almost certain that a class of phenomena existed, only to have it shown empirically that it does not exist? We have to find the cracks in our knowledge, rather than making random choices.

You say that we can describe the world only from a particular perspective. Doesn’t that make reality subjective?

Perspectivalism does not mean subjectivity. That is the point. There is nothing special about humans. We are just physical systems, like anything else. Yes, any account of reality needs to have a perspective, but it doesn’t need to be a human one. The Moon has one velocity with respect to Earth and a different velocity with respect to the Sun. It’s all relational. Not because there is a human observing it, but because velocity really is relative.

How might such a view change our thinking?

For me, the key is quantum mechanics. The theory works really well, but it is still confusing. There are several ways to make sense of quantum mechanics, and they can be divided into two classes. One involves theories that assume a framework of knowledge beyond what we can see (such as the many-worlds, universal-wave-function and hidden-variables theories).

The alternative, which I think is more scientifically fruitful and reasonable, says that quantum mechanics is telling us something deep about the world, namely that you should not ask what is really, really going on, because that’s a bad question.

What could convince you that your interpretation is wrong?

One way would be to make an experiment that contradicts quantum mechanics. But it is often not crucial experiments that decide what we think is true. It’s a piling up of evidence. Some ways of thinking show themselves to be much more fruitful than others. Science is not only writing equations, checking predictions and discarding equations that give incorrect predictions. It also means evolving our general conceptual structure.