As formally introduced by Physicists David Deutsch in 2012, Constructor theory "seeks to express all fundamental scientific theories in terms of a dichotomy between possible and impossible physical transformations – those that can be caused to happen and those that cannot."
Constructor Theory recognises that "the empirical content of a scientific theory is in what it forbids." This respects the way scientific principles (e.g. of the conservation of energy) allow us to rule conceivable transformations (counterfactuals) as either conceivable or as simply incompatible with what we understand about how the universe works.
The language of Constructor Theory breaks significantly with traditional physics. Key concepts include:
Tasks and Counterfactuals
At the heart of Constructor Theory we find Tasks. These are possible (or impossible) physical transformations. A counterfactual is simply an imagined physical transformation (specifying a task which would need to be completed).
For Physicists David Deutsch and Chiara Marletto, constructors are identified functionally by their capacity for catalysing some form of transformation and of remaining able to cause new (further) transformations.
In Constructor Theory, anything which can be transformed features as substrate. Any task must, by definition, transform some substrate from a prior state to a transformed state. Specifying any task therefore requires identification of some input attribute of a substrate and some output attribute of a substrate.
Constructor Theory of Information
David Deutsch and Chiara Marletto talk of knowledge as an "abstract constructor." For discussion see The Constructor Theory of Information.
The Constructor Theory of Probability
The Constructor Theory of Life
Constructor Theory of Cognition
In cognitive context, the constructor is a subject who thinks. A subject for example can simply think, or he can make a choice or give an answer: all these situations cause a transition of belief. In other situations, the interaction is with an external system, also called environment, like for example another subject or an object. The subject is able to perform again cognitive processes leaving unchanged such ability, of course with human limits imposed by attention and physical resources.— Riccardo Franco, First steps to a constructor theory of cognition, arXiv:1904.09829 [cs.AI]