 The assumption that facts contain objects, properties and relations as proper parts may be criticised (Lowe 1998; Vallicella 2000; Künne 2003). One natural mereological principle is that the proper parts of the most basic kinds of whole belong to the same general ontological category to which their wholes belong. Thus parts of things or substances are things or substances and parts of processes are processes. The view that the fact that Sam is sad contains a substance and a property offends against this principle: substances and properties belong to different kinds and neither substances nor properties, it seems, are facts. Perhaps the natural mereological principle should be rejected in favor of the view that entities of any kind may come together to form a whole. But friends of facts tend to think of facts as forming a very natural kind of whole. Another possible view is that Sam is a fact rather than part of a fact (Armstrong 1997; Johansson 2004: 34; Récanati 2000; Bergmann 1967).