Full Idea
Whether my body weight is necessary or contingent makes no difference at all to my causal powers, so modality is epiphenomenal; if you took causal potential as a test of reality you would have to declare modes unreal.
Gist of Idea
If causal power is the test for reality, that will exclude necessities and possibilities
Source
Colin McGinn (Logical Properties [2000], Ch.4)
Book Reference
McGinn,Colin: 'Logical Properties' [OUP 2003], p.86
A Reaction
We could try analysing modality into causal terms, as Lewis proposes with quantification across worlds, or as Quine proposes by reduction to natural regularities. I am not sure what it would mean to declare that modes are 'real'.