Date of Award

May 2020

Degree Type


Degree Name

Master of Arts



First Advisor

Joshua Spencer

Committee Members

Michael Liston, Peter van Elswyk


Lewis, Metaphysics, Modality, Truthmakers


Lewisian modal realism is infamous for explaining the objectivity of modal discourse in terms

of concrete possible worlds. Many have developed alternative theories which seek to explain

the objectivity of modal discourse without concrete possible worlds. One such alternative,

due to Fabrizio Mondadori and Adam Morton, attempts to ground modal discourse in actual,

physical fact. Shockingly, Lewis seems to have claimed that their view is consistent with his

own. I argue that the two views are consistent, from Lewis’s perspective. The result of the

project is twofold. First, we see that in Lewisian realism intrinsic features of the actual world

are a necessary component (i) for making modal propositions true in the actual world and (ii)

for causally explaining how modal events would occur, if they did. Second, this insight

motivates a rejection of the classic ‘Humphrey objection’ to counterpart theory, and

ameliorates the worry that Lewis’ possible worlds somehow “change the subject”.

Included in

Metaphysics Commons