  After 1-point compactification, the collection of all unordered configuration
spaces of a manifold admits a commutative multiplication by superposition of
configurations. We explain a simple (derived) presentation for this commutative
monoid object. Using this presentation, one can quickly deduce Knudsen's
formula for the rational cohomology of configuration spaces, prove rational
homological stability, and understand how automorphisms of the manifold act on
the cohomology of configuration spaces. Similar considerations reproduce the
work of Farb--Wolfson--Wood on homological densities.
