The bundle theory construes objects as collections of properties (tropes or universals)
tied together by a bundling relation, often called
"compresence". It opposes to the substratum theory, the view
that objects are substrates instantiating properties or having modes. One can
distinguish between two interesting debates.
First, it can be disputed which of the two views
should be preferred. A classical objection against
the bundle theory is the objection from change advocated by Van Cleve. He argues that a bundle cannot change
its members without becoming another bundle, and
thus, another individual. Another interesting problem has to do with the
bundling relation: what is it? Is it a primitive sui generis relation,
or can it be identified with another relation,
already present in one's ontology?