Constructor theory is a proposal for a new mode of explanation in fundamental physics in the language of ergodic theory, developed by physicists David Deutsch and Chiara Marletto, at the University of Oxford, since 2012. Constructor theory expresses physical laws exclusively in terms of which physical transformations, or tasks, are possible versus which are impossible, and why. By allowing such counterfactual statements into fundamental physics, it allows new physical laws to be expressed, such as the constructor theory of information.