Full Idea
The metaphysician has no test for the truth of her beliefs except that other metaphysicians can't think of obviously superior alternative beliefs. (They can always think of possibly superior ones, in profusion).
Gist of Idea
There is no test for metaphysics, except devising alternative theories
Source
J Ladyman / D Ross (Every Thing Must Go [2007], 1.7)
Book Reference
Ladyman,J/Ross,D: 'Every Thing Must Go' [OUP 2007], p.58
A Reaction
[they cite Van Fraassen for this view] At least this seems to concede that some metaphysical views can be rejected by the observation of beliefs that are superior. Almost everyone has rejected Lewis on possible worlds for this reason.