Diving into the sea of counterfactuals
What is constructor theory?
Constructor theory is a way of expressing all fundamental scientific theories using the idea of possible and impossible physical transformations. Those that can be made to happen and those that cannot. This is the deviation from the widespread conception of fundamental physics which works by predicting how the system is going to evolve starting from initial conditions and following specific laws of motion. But you might ask, why should we even try to challenge this traditional understanding of physics? Oftentimes, it may look like we unraveled all of nature’s little secrets, that we figured out all the formulas. But anyone within the scientific community would know that this is not the case. As a matter of fact, we still have a very long way to go despite all the progress physics made so far. Some problems that have been left unsolved for several decades now need attending to. This is why scientists have been working together and collaborating to try changing the tools that are used to address these problems.
What is the motivation behind this new theory?
Numerous subsequent motivations are discussed for expecting constructor theory to become one of the fundamental branches of physics. The theory’s potential for solving a myriad of problems and achieving unprecedented advancement in the unification of all laws of physics is being explored. Amongst them, we can site :
- a theory of information concealed at the basis of both classical and quantum information;
- extending the theory of computation to encompass all physical transformation;
- combining formal statements of the laws of conservation with stronger operational ones (for example, because of the law of energy conservation we can exclude the possibility of existence of perpetual motion machines);
- granting exact statements of emergent laws (like the second law of thermodynamics for instance);
- and expressing in terms of physics certain attributes that are deemed anthropocentric or metaphysical (such as knowledge).
The difference between conventional physics and constructor theory
This is how physics usually functions:
- You start with what we see, with our experiences, with what exists in the world around us,
- Afterwards, physics attempts to come up with explanations, and it sort of explains that in terms of things that occur, either in the past or that will happen on the future.
Everything boils down to the same mode of explanation. Explaining things in terms of trajectories and particles in space and time has been the approach taken since Galileo’s breakthroughs and Newton’s laws. Of course this method of explanation has been extremely fruitful for quite a long time and had heaps of extraordinary revelations appended to it. For example, Maxwell’s laws to describe light, and of course the quantum theory and general relativity which aren’t that different either from all the classical physics at their source, even Schrödinger's wave equation is about the evolution of something across space and time. Regardless of how successful physics has been up to this point, there are things that you can’t quite fit into these models.
In order to dive deeper into what exactly is this new theory that claims to rewrite physics, we need to introduce counterfactuals.
They are things that are fundamental to our understanding of the world around us, both at the everyday level and at the level of the most important phenomena in physics, yet they have customarily been viewed as difficult to fuse into the fundamental scientific method and that have so far been neglected. They are facts, not with regards to what is (the “actual”), but rather concerning what physical event could or couldn’t be made to happen. In an effort to discern between them and the actual, they are called counterfactuals.
For instance, a counterfactual property forced by the laws of physics is that it is impossible to build a perpetual motion machine.
A perpetual motion machine is not just an object that moves forever once set into motion: it must also generate useful work. If this device could exist, it would produce energy out of no energy. It could be exploited to make your car run perpetually without using fuel of any kind. Any succession of changes transforming something without energy into something with energy, without draining any energy supply, is impossible in our universe: it could not be made to happen, and that is explained by the principle of conservation of energy.
This is a significant takeoff from the traditional conception of physics and science in general, which takes for granted the fact that scientific theories must be regarding what must occur in the universe (or what is probably going to), considering what already happened, and which rejects something as intangible as causation and free will. And it even characterizes such fundamental laboratory ideas as temperature, information, and computation as being at odds with any exact depiction of nature, and advantageous just at the level of human sensory experience. In any case, no part of that is valid. Those are close to self-assertive restrictions on our capacity to comprehend the world. Luckily, they are generally mocked both in everyday life and in theoretical physics, yet frequently culpably and regretfully. Assuming something is incompatible with the conventional conception doesn’t make it incompatible with precise scientific description. It’s only that in those cases, careful depictions require leaving the traditional ideas, it requires counterfactuals.
Prelude on Information
Something is able to hold information given that its state could have been different. Take a PC memory for example. It is absolutely useless if the factory foreordained every one of its changes and progressions in content over time, the client could not store anything in it. And this also applies if we were to replace “factory” with the Big Bang.
This leads us to introduce two very important concepts in constructor theory, which are “information” and “knowledge”.
Information and Knowledge
There are two counterfactual properties that make a physical system capable of carrying information :
1. It can be set to any of at least two states. (The flip operation is possible, according to the laws of physics)
2. Each one of those two states can undergo the copy operation. (It is possible, according to the laws of physics).
Here is the reason why ‘information’ is considered as a physical property: the ability of a system to carry information will depend on whether the laws of physics allow those two transformations on that system. If they don’t, then the system is incapable of carrying information.
So whether or not information is allowed relies on whether the laws of physics allow specific sorts of counterfactuals. Through counterfactuals, you have arrived at the slippery but legitimate association between information and physics!
As for knowledge, it is said that any transformation that occurs reliably requires a generalized catalyst, an entity that is able to perform the transformation and retain the ability to cause it again. Any catalyst must contain an abstract catalyst, which consists of knowledge.
Knowledge is like a constructor that is capable of self-preservation. For example, this can be applied directly to DNA and genes: Neo-Darwinian evolutionary theory explains how the presence of purposive design in the adaptations of living organisms can have occurred without their purposefully being designed. The explanation resides essentially in the possibility of certain physical processes: mainly, gene replication and natural selection. They applied constructor theory’s new mode of explanation to express exactly and within the scope of physics, the appearance of design, no-design laws, and the logic of self-reproduction and natural selection. It has been concluded that self-reproduction, replication and natural selection are possible under no-design laws, with the condition that they allow digital information to be physically instantiated. This shows exact resemblance with the constructor theory of information and also proves that the accurate replication of the information stored in genes requires the existence of a vehicle constituting, together with the replicator, a self-reproducer, which is also mainly referred to as Knowledge.
There is still much to know about constructor theory and all the areas of science it will permit us to understand exactly, to site just a few there is Quantum information and Quantum computing, as well as the theoretical design of a Universal computer, first imagined by John von Neumann, capable of performing all the computations permitted by the laws of physics, including replicating itself, and also everything regarding the unification of the laws of physics with the help of the quantification of gravity.
Constructor Theory recasts physics into a new form capable of tackling these deep questions like “What is information?” or “What makes complex life forms possible?”. It is believed that constructor theory has the potential to change the way we think about the universe and our own place within it.
— Chiara, Marletto. The Science of Can and Can’t: A Physicist’s Journey through the Land of Counterfactuals.Penguin Publishing Group (2021)
— David, Deutsch. (11 April 2013) ”The Philosophy of Constructor Theory“. Synthese, Volume 190, Issue 18. Centre for Quantum Computation, University of Oxford. From (https://www.constructortheory.org/portfolio/the-philosophy-of-constructor-theory/)
— Chiara, Marletto. (06 March 2015) “Constructor theory of life”. Volume 12 Issue 104. Published by: Royal Society. From (https://royalsocietypublishing.org/doi/10.1098/rsif.2014.1226)
— Simon, Benjamin. (Apr 4, 2015) “Constructor theory”. Youtube, from (https://youtu.be/8DH2xwIYuT0)
— The Royal Institute. (Sep 7, 2021) “Constructor Theory: A New Explanation of Fundamental Physics — Chiara Marletto and Marcus du Sautoy”. Youtube, from (https://youtu.be/zFm-5uqvMWk)