Constructor theory

In his Constructor Theory paper, David Deutsch posits that the goal of the theory is to frame all fundamental scientific theories in terms of a dichotomy between physical transformations that can be caused to occur and those that cannot. David Deutsch notes that this is a deviation from the prevailing conception of fundamental physics, which is concerned with predicting what will occur based on initial conditions and laws of motion.

Introduction to constructor theory

In constructor theory, physical laws are formulated exclusively in terms of tasks that are possible (based on the factors of accuracy, reliability, and repeatability) and those that are impossible—as opposed to what happens or doesn't happen, given dynamical laws and conditions. A task is considered impossible if there is a law of physics that forbids it. Otherwise, it is considered possible, which means that a constructor for that task can be approximated arbitrarily well in reality. David Deutsch defined constructors as objects that cause tasks to occur and retain the ability to cause them again. For instance, factories, robots, and living cells are all accurate approximations to constructors.

In an article published by The Royal Society, Chiara Marletto applied constructor theory to articulate the appearance of design, no-design laws, and the logic of self-reproduction and natural selection within physics. She concluded that self-reproduction, replication, and natural selection are possible under no-design laws so long as they allow digital information to be physically instantiated. According to Chiara Marletto, this hypothesis has an exact characterization in the constructor theory of information. In addition, she demonstrated that under no-design laws, an accurate replicator necessitates the existence of a "vehicle" that combines with the replicator to constitute a self-reproducer.

David Deutsch and Chiara Marletto have collaborated on developing a theory that applies the tenets of constructor theory to information. This proposed theory, called the constructor theory of information, expresses the regularities that allow information to be physically instantiated through conjectured, exact laws of physics. Within this hypothesis, information is regarded as something with nature and properties that are determined only by these laws, and not as an a priori mathematical or logical concept.

According to Deutsch and Marletto, this theory solves a foundational problem of prevalent information theory that defines information and distinguishability each in terms of the other. In addition, it elucidates the link between classical and quantum information and how what the authors term “constructor-theoretic property” underlies the most distinctive phenomena related to the latter, including the impossibility of cloning; the simultaneously deterministic and unpredictable nature of measurement processes; perturbation caused by measurement; and locally inaccessible information, such as that of systems in the state of quantum entanglement.

Chiara Marletto has stated,

The language of constructor theory gives a natural way to describe the most fundamental principles that must be obeyed by all subsidiary theories, like conservation of energy.

Furthermore, she elaborated that in this example, the process is begun by stating "that the task of creating energy from nothing is impossible.”

Dean Rickles, a philosopher of physics at the University of Sydney who was not involved in the development of the theory, said “In principle, everything possible in our universe could be written down in a big book consisting of nothing but tasks [and in] this big book will also be encoded all of the laws of physics.” The theory remains unverified and it is not known whether it is successful in its objective of uniting classical and quantum information theory. Rickles opined that constructor theory has the potential to prescribe meta-laws that general relativity and quantum theory must obey.