Logic of logic and the logic of dreams.

For Bateson explanation is the mapping of description onto tautology. "An explanation has to provide something more than a description provides, and in the end, an explanation appeals to a tautology, which as I have defined it, is a body of propositions so linked together that the links between the propositions are necessarily valid. A tautology in its simplest form is ‘If P is true, then P is true.'" Tautologies can be very elaborate including, for example, systems of nonlinear dynamical equations. Descriptions include all the data (field notes and measurements) that scientists take when studying some phenomena. This mapping of formal models onto observable data can yield powerful insights and is what ateson defines as explanation. The tautological relations within the mathematical model are mapped to relations observed in nature.