Full Idea
The thesis of 'expressibility' says that for all being, there is a proposition (perhaps one never formulated by any mind at any time) that truly renders the existence and nature of this being.
Gist of Idea
For all being, there is a potential proposition which expresses its existence and nature
Source
David M. Armstrong (Truth and Truthmakers [2004], 02.3.2)
Book Reference
Armstrong,D.M.: 'Truth and Truthmakers' [CUP 2004], p.9
A Reaction
[He credits Stephen Read 2000:68-9 for this] Armstrong accepts this, but I deny it. I can't make any sense of this vast plethora of propositions, each exactly expressing some minute nuance of the infinity complexity of all being.