This chapter considers Hylas’ various notions of matter as candidates for intermediary entities standing between God and sensible qualities. These are characterized first as ‘cause’, then ‘instrument’, and then ‘occasion’. Philonous rejects all these which forces Hylas to put forward a content-less account of matter as ‘something in general’. This leads to a discussion of material substance in Plato, Descartes and Locke and to a consideration of how Berkeley understood the limits of thought.