Kinds, Composition and the Identification Problem
Elbert J. Booij

Abstract:
Kinds - also known as 'natural sets' or 'universals' - are a very
intuitive assumption about the way the world is put together. As a
piece of metaphysical theory, however, they give rise to the
Identification Problem: which of all sets are the ones that in fact
qualify as kinds? In this thesis an answer is given starting out from
the assumption that kindhood always coincides with similarity. From
this it follows that similarity must be similarity 'with respect to',
and p properties - kinds - must be arranged in 'similarity systems'.

To turn this insight into a credible answer to the Identification
Problem, however, a wide variety of (physical) objects must be
considered, whose common ground is that they are all 'mereologically
complex'. Therefore in the second part of the thesis the focus will be
on the derivation of 'composite kinds', thus allowing the
classification of larger objects in terms of kinds. It will be
concluded that classical (Boolean) mereology is sufficient for this
purpose. I shall argue that this approach is therefore preferable to
that whereby kinds are reified to be (structural) universals.