ABSTRACT
Locke's critics tend to make a second mistaken assumption about the ontological categories to which various subjects of identity are assigned especially the category of substance. The obscures differences in the metaphysical make-up of things which affect their status as bearers of qualities and subjects of identity over time. Porphyry's widely accepted scheme was designed for an Aristotelian theory of substance. Mechanists maintain a contrary doctrine, that matter, that is, the stuff of which material things are made, is the substance. The diversity of qualities and powers exhibited by sensible material things rather than having a source within substance is due entirely to affections, contingent modifications which depend for their existence on substance. Sensible material things exhibit a variety of colours and other secondary qualities, as well as tendencies to produce specific effects and to be affected by specific agents. Textures are relatively stable coherent arrangements which regiment the motions of particles in ways that affect their joint effects.
