Full Idea
Armstrong offers 'totality facts' (complete states of affairs) as truthmakers for negative existentials, and for negated predications.
Clarification
A 'negative existential' denies the existence of something
Gist of Idea
Negative existentials have 'totality facts' as truthmakers
Source
report of David M. Armstrong (A Combinatorial Theory of Possibility [1989]) by David Lewis - Armstrong on combinatorial possibility 'The demand'
Book Reference
Lewis,David: 'Papers in Metaphysics and Epistemology' [CUP 1999], p.205