This question is closely related to this previous question.
Chern and Stiefel-Whitney classes can be defined on bundles over arbitrary base spaces. (In Hatcher's Vector Bundles notes, he uses the Leray-Hirsch Theorem, which appears to require paracompactness of the base space. The construction in Milnor-Stasheff works in general, as does the argument given by Charles Resk in answer to the above question. A posteriori, this actually shows that Hatcher's construction works in general too, since he really just needs
$c_1$ to be defined everywhere.)
The proof of uniqueness (as discussed in Milnor and Stasheff, or in Hatcher's Vector Bundles notes, or in the answers to the above question) relies on the splitting principle, and hence (it seems to me) requires the existence of a metric on the bundle in question. More precisely, if we have two sequences of characteristic classes satisfying the axioms for, say, Chern classes, and we want to check that they agree agree on some bundle
$E\to B$, the method is to pull back
$E$ along some map
$f: B'\to B$ (with $f^*$ injective on cohomology) so that
$f^*E$ splits as a sum of lines. Producing the splitting seems to require a metric on
$E$ (or at least on
$B$ is not paracompact, bundles over
$B$ may not admit a metric (and may admit a classifying map into the universal bundle over the Grassmannian), so my question is:
Are Chern and/or Stiefel-Whitney classes unique for arbitrary bundles? If not, do
$c_1$ at least determine the higher-dimensional classes?