My understanding is that this is more of an approach than a single rigorous theory. Modern theories typically define operators that are applied to a current sta

My understanding is that this is more of an approach than a single rigorous theory. Modern theories typically define operators that are applied to a current state to derive a future state; constructor theory skips all of that and says that some start -> finish pairs are allowed and some forbidden. Conservation of energy is very much of this model: it doesn't say why or how it's conserved, but from it you can figure out things like the velocity an object gains as it moves through a gravitational potential.