The Physics of Counterfactuals: Applications of the Constructor Theory of Information to Thermodynamics, the Physics of Time and Quantum Information

Constructor theory is a radical new approach to physics.

The traditional reductionist conception of physics resorts to predictions given initial conditions and dynamical laws. This approach has been successful since the times of Galileo and Newton. Although very successful in countless cases, this mode of explanation falls short in capturing certain elements of physical reality. Famous examples include information, heat, and entropy. In the prevailing conception, these entities appear in what look like fundamental laws—for example, the laws of the theory of computation and thermodynamics. But reconciling or unifying such laws with other microscopic fundamental laws is notoriously problematic, as they have only coarse-grained, scale-dependent forms.

Taking a sharp departure from such approaches, constructor theory (CT) expresses laws as statements about which physical transformations are possible and impossible—and why. Designed to accommodate counterfactuals in fundamental physics in an exact manner, CT supplements the prevailing conception. In the bigger picture, CT has three goals:

1. To provide a unifying and deeper understanding of physical reality;
2. to develop new tools and identify new laws underpinning emergent entities (e.g., agency, free will, and knowledge-creation); and
3. to permit a broader kind of scientific inquiry that contrasts with mere reduction to dynamical laws and initial conditions.

Supported by the Templeton World Charity Foundation, D. Deutsch (CT's originator) and Dr. Chiara Marletto completed a groundbreaking three-year project that elicited great interest from popular press. In this new project, Marletto will apply their constructor-information-theoretic approach to fundamental problems in three different areas:

1. Thermodynamics
2. the physics of time; and
3. quantum information.

The project will develop information-theoretic laws about counterfactual entities in those areas (like heat) that have been long-considered emergent and not fundamental. Doing so will show the power of information in fundamental physics. The project also seeks to establish CT as a positive framework for science at large—one in which everything that is not physically impossible can be achieved. Constructor Theory provides a basis in fundamental physics for the freedom to become “all that we can be,” opening our minds to those endless possibilities permitted by the laws of physics.