  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. This is a departure
from the prevailing conception of fundamental physics which is to predict what
will happen from initial conditions and laws of motion. Several converging
motivations for expecting constructor theory to be a fundamental branch of
physics are discussed. Some principles of the theory are suggested and its
potential for solving various problems and achieving various unifications is
explored. These include providing a theory of information underlying classical
and quantum information; generalising the theory of computation to include all
physical transformations; unifying formal statements of conservation laws with
the stronger operational ones (such as the ruling-out of perpetual motion
machines); expressing the principles of testability and of the computability of
nature (currently deemed methodological and metaphysical respectively) as laws
of physics; allowing exact statements of emergent laws (such as the second law
of thermodynamics); and expressing certain apparently anthropocentric
attributes such as knowledge in physical terms.
