  Intuitively speaking, a classical field theory is background-independent if
the structure required to make sense of its equations is itself subject to
dynamical evolution, rather than being imposed ab initio. The aim of this paper
is to provide an explication of this intuitive notion. Background-independence
is not a not formal property of theories: the question whether a theory is
background-independent depends upon how the theory is interpreted. Under the
approach proposed here, a theory is fully background-independent relative to an
interpretation if each physical possibility corresponds to a distinct spacetime
geometry; and it falls short of full background-independence to the extent that
this condition fails.
