 The arguments addressed to RT turn out to show that a quality is real just in case it resembles the idea of it. Essay 2.8, sections 17 and 18 explicitly state that PQs are real qualities, i.e. qualities that are in a body whether it is perceived or not, and SQs are not real qualities; the point is reiterated in sections 22 and 23. Rickless takes the emphasis on reality and non-reality to show that for Locke, the most fundamental difference between PQs and SQs is that the former are real qualities of bodies and the latter are not in the strictest sense. We can suggest that although this may be the basic difference from the perpective of natural philosophy, Locke’s interest in the P/SQ distinction derives from his more fundamentl interest in the relation between perception and reality (see E 2.8.7, .22), From Locke’s perpective, the basic difference is at the level of sorts of ideas of sensation and the difference has to do with how they represent the real qualities present in bodies perceived by the senses.