Full Idea
'Non-transferable' theories of tropes hold that the mass is of this stone by necessity. It is an identity condition for the property. Every property then becomes an essential property.
Gist of Idea
If tropes are non-transferable, then they necessarily belong to their particular substance
Source
David M. Armstrong (Truth and Truthmakers [2004], 04.3)
Book Reference
Armstrong,D.M.: 'Truth and Truthmakers' [CUP 2004], p.46
A Reaction
[He cites Martin and Heil for this view] It is hard to see in this proposal how the trope is in any way separate from its substance, and hence it seems a bit of a vacuous theory. (The other theories of properties aren't much cop either).