Over at Edge.org Chiara Marletto talks about constructor theory in physics. Concerning how a bacterium uses DNA to construct an exact duplicate of itself:
The key to the way a bacterium performs its own self-reproduction (under laws that do not contain the design of biological adaptations) is the same as the key to the way, say, a car factory constructs a car. In both cases there is a recipe—a bit of information—that has the ability of directing a construction process, of causing a task to be performed because it contains the knowledge about how to perform it by following elementary, non-specific steps. In the case of the bacterium, it is the DNA sequence of the bacterium and, in the case of the car factory, it is the sequence of elementary steps to assemble a car out of elementary components.This particular kind of information, this recipe, can also have an exact characterization in constructor theory, as knowledge: it is information that can act as a constructor—i.e., an object that can cause transformations and retain the property of causing them again. All these elements that I just mentioned—information, knowledge—are emergent things that, in the prevailing conception of fundamental physics, would not have a natural expression because you would have to talk about many atoms undergoing certain complicated transformation in some phase space; while in constructor theory, they are natural objects. They are the very elements by which the theory expresses itself. These are examples of how constructor theory brings in conceptual 'devices' that are new to physics, so that it can address problems that have been not solved so far. That's very promising.
As for human beings:
It turns out that in the constructor theoretic view, humans, as knowledge creating systems, are quite central to fundamental physics in an objective, non-anthropocentric, way. This is a very deep change in perspective. One of the ideas that will be dropped if constructor theory turns out to be effective is that the only fundamental entities in physics are laws of motion and initial conditions. In order for physics to accommodate more of physical reality, there needs to be a switch to this new mode of explanation, which accepts that scientific explanation is more than just predictions. Predictions will be supplemented with statements about what tasks are possible, what are impossible and why.
Constructor theory seems to be a kind of meta-theory, and metaphysics?
One question might be how do you test constructor theory? Well, constructor theory has a status that is that of underlying theories like quantum theory, general relativity, and possibly others, maybe better ones. It's more fundamental than those and it underlies them, and the way it does so is by being a theory of principles. It expresses statements that are a bit like the principle of conservation of energy, statements that constrain theories, so some theories are just incompatible with constructor theory, with its principles.As I said, constructor theory informs the experiments not in a direct way because it doesn’t make predictions directly, but it provides principles. Just like you would go about testing certain principles such as the conservation of energy, you can in fact indirectly test constructor theory by testing the theories that obey it.
Von Neumann seems to be a precursor:
That is a different perspective—the constructor theoretic way of explaining things. Von Neumann, when thinking about self-reproduction—he pioneered the idea that self-reproduction must occur in two steps: by first copying what we call now the DNA sequence coding for the organism, and then by executing the recipe that is inside the DNA to construct a new instance of the organism—did not use the mode of explanation by predictions in order to explain this. He used a computational model to simulate this process. He had an understanding that this was a fundamentally different question from one that you would answer by only making predictions.