Full Idea
A proper ontology should invoke only categorical, or occurrent, properties and relations. Categorical properties involve what objects are actually like, whereas hypothetical properties 'point beyond' their instances.
Gist of Idea
Proper ontology should only use categorical (actual) properties, not hypothetical ones
Source
Theodore Sider (Four Dimensionalism [2001], 2.3)
Book Reference
Sider,Theodore: 'Four Dimensionalism' [OUP 2003], p.41
A Reaction
This spectacularly leaves out powers and dispositions, which are actual properties which 'point beyond' their instances! This is the nub of the powers debate, and the most interesting topic in modern metaphysics.