"In this brief paper I develop and defend a 
novel answer to Peter Van Inwagen’s Special 
Composition Question (SCQ), namely, under what 
conditions do some things compose an object? 
My answer is that things will compose an 
object when and only when they exist 
simultaneously, relative to a reference frame 
(I call this ‘Temporally Restricted Mereology, 
or TREM). I then show how this view wards off 
objections frequently given by the Unrestricted 
Mereologists to any restriction on composition. 
TREM does not succumb to arguments from 
vagueness, anthropocentricism, or arbitrariness. 
TREM also has advantages over rival restrictions 
on composition, such as Nihilism, Organicism, 
and Intuitivism. Lastly, TREM has significant 
advantages over Unrestricted Mereology in not 
admitting a bevy of cross-time fusions, and helps 
support Three Dimensionalism.
"