  The history of general relativity suggests that in absence of experimental
data, constructing a theory on philosophical first principles can lead to a
very useful theory as well as to ground-breaking insights about physical
reality. The two related concepts of general covariance and background
independence are some of these principles and play a central role in general
relativity. A definition for them will be proposed and discussed.
  Constructing a theory of quantum gravity -- the sought-after unification of
general relativity and quantum mechanics -- could profit from the same
approach. Two popular research areas of quantum gravity, string theory and loop
quantum gravity together with spin foams, are being examined whether they
comply with these principles.
