Solving the mysteries of the universe is usually about finding the best answer to a question. But what if we are not even asking the right questions?

A pioneer in quantum computation, University of Oxford physicist and best-selling author David Deutsch has spent most of his career working towards a new way of asking questions about the universe. Deutsch’s vision for this “theory of everything” ties together ideas in cosmology, computation, philosophy and evolution to describe the nature of reality.

It has been suggested that his long-awaited theory could account for several fundamental mysteries, such as why time flows in only one direction – a property that is not required by most physical laws. Now Deutsch has posted a taste of the form his theory might take, opening the door to what may become a new branch of physics.

Transformations rule

According to Deutsch, the problem with current theories is that they do not adequately explain why some transformations between states of being are possible and some are not. We know, for instance, that dye can dissolve in water and cannot spontaneously clump back together – but we do not know why that must be so.


Deutsch proposes a framework built on the transformations themselves, rather than the components. Called Constructor Theory, this model defines a constructor as anything that causes transformations in physical systems without itself being altered, rather like a chemical catalyst. Deutsch then asks which transformations must be ruled out to achieve a particular result, regardless of the constructor that caused it. In other words, which processes can happen to cause dye to dissolve in water, which ones cannot, and why?

Deutsch’s vision can be seen as a generalisation of the second law of thermodynamics, says Vlatko Vedral, also at Oxford. This law encompasses the property of entropy, which says that order leads to disorder in a closed system. Entropy, in turn, implies that we cannot rewind time, because that would involve disordered matter moving towards order.

In Constructor Theory, the key would be figuring out why such a transformation would not be allowed. In asking those types of questions, Deutsch seems to want to apply the notion that some states are simply inaccessible from others to all physical laws, Vedral says.

Laying that groundwork might explain, for instance, why the laws of quantum mechanics are so strict, says Vedral. Small variations in the way we describe quantum laws can lead to contradictions, such as a violation of the speed of light.

“As soon as you modify quantum mechanics, something goes wrong,” he says. “Why is this? It’s a puzzle.” If Constructor Theory can show which transformations are permitted and which are not, that would explain the very underpinnings of quantum mechanics, says Vedral.

Stated intent

“It’s tricky to see what this would look like,” he admits. And for now, the new paper on Constructor Theory is only a statement of intent, says Vedral. “It’s not yet at the level where you can recover existing physics.” But he is excited about the possibilities.

What Deutsch seems to be reaching for is a theory that goes beyond a computational view of the universe, says Seth Lloyd at the Massachusetts Institute of Technology in Cambridge. Such a theory might not only help unify relativity and quantum mechanics, it might also show that they are necessary parts of the universe, answering the troubling philosophical question of why things are the way they are, he says.

“If Deutsch can do that, it would be awesome,” adds Lloyd.

Journal reference: arxiv.org/abs/1210.7439