  By a uniform and simple Weyl invariant coupling of scale and matter fields,
we construct theories that unify massless, massive, and partially massless
excitations. Masses are related to tractor Weyl weights, and
Breitenlohner-Freedman stability bounds in anti de Sitter amount to reality of
these weights. The method relies on tractor calculus -- mathematical machinery
allowing Weyl invariance to be kept manifest at all stages. The equivalence
between tractor and higher spin systems with arbitrary spins and masses is also
considered.
