  This is a conceptual paper that re-examines the principles underlying the
application of renormalization theory to quantum phase transitions in the light
of quantum information theory. We start by describing the intuitive argument
known as the Kadanoff ``block-spin'' construction for spins fixed on a lattice
and then outline some subsequent ideas by Wilson and White. We then reconstruct
these concepts for quantum phase transitions from first principles. This new
perspective offers some very natural explanations for some features of
renormalization theory that had previously seemed rather mysterious, even
contrived. It also offers some suggestions as to how we might modify
renormalization methods to make them more successful. We then discuss some
possible order parameters and a class of functionals that are analogues of the
correlation length in such systems.
