  Topos approaches to quantum foundations are described in a unified way by
means of spectral bundles, where the base space is a space of contexts and each
fibre is its spectrum. Differences in variance are due to the bundle being a
fibration or opfibration. Relative to this structure, the probabilistic
predictions of the Born rule in finite dimensional settings are then described
as a section of a bundle of valuations. The construction uses in an essential
way the geometric nature of the valuation locale monad.
