Formulating Science in Terms of Possible and Impossible Tasks


A Conversation with Chiara Marletto over at

I’ve been thinking about constructor theory a lot in the past few years. Constructor theory is this theory that David Deutsch proposed—a proposal for a new fundamental theory to formulate science in a completely different way from the prevailing conception of fundamental physics. It has the potential to change the way we formulate science because it’s a new mode of explanation.

When you think about physics, you usually describe things in terms of initial conditions and laws of motion; so what you say is, for example, where a comet goes given that it started in a certain place and time. In constructor theory, what you say is what transformations are possible, what are impossible, and why. The idea is that you can formulate the whole of fundamental physics this way; so, not only do you say where the comet goes, you say where it can go. This incorporates a lot more than what it is possible to incorporate now in fundamental physics.

David and I have been working on this together for the past three years, and we’ve been applying it to many different problems. So far, the two completed parts of our trying out constructor theory to see whether it can solve problems are: a fundamental theory of information within physics1; and the constructor theory of life2, which applies this new theory of information to a fundamental problem that's at the boundary between physics and biology, and has to do with how certain features of living things, such as the ability to self-reproduce very accurately, are compatible with the laws of physics as we know them.

In these two cases, you can see how switching to this new mode of explanation allows one to change the perspective and address the problems in a much more effective way. These are two examples where switching to this new mode of explanation makes all the difference.

Take information, for example. Information is something we use in our everyday speaking; also we use it in physics a lot. For instance, we assume that information has certain properties, e.g. that it can be copied from one physical system to another. So far, we did not have a fundamental theory telling us what are the regularities in nature that allow the existence of information in this sense. But whenever we talk about information we refer to those regularities. We assume, for example, that the laws of physics allow copy processes. In constructor theory you can express these regularities, and this is what our theory does. Our way of incorporating information in fundamental physics is by formulating what are these regularities in nature that allow the existence of information.

More here.