Full Idea
We can't define mass in terms of its causal powers because massive objects do different things in different physical systems. …What an object (or concept) with a given property does depends on what it interacts with.
Gist of Idea
Even 'mass' cannot be defined in causal terms
Source
Gabriel M.A. Segal (A Slim Book about Narrow Content [2000], 4.1)
Book Reference
Segal,Gabriel M.A.: 'A Slim Book about Narrow Content' [MIT 2000], p.97
A Reaction
This leaves an epistemological problem, that we believe in mass, but can only get at it within a particular gravitational or inertial system. Don't give up on ontology at this point.