KNOWLEDGE It would be tedious to follow, line by line, the sleight of hand by which Hylas is tricked into denying the objectivity not only of heat, but of tastes, odours, sounds, and colours Halfway through the dialogue, Hylas concedes that secondary qualities have no existence outside the mind But he tries to defend Locke’s position that primary qualities really exist in bodies Philonous is now in a strong position to show that the arguments used by Locke to undermine the objectivity of secondary qualities can also be deployed against primary qualities Locke had argued that odours were not real properties because things that smell foul to us smell sweet to animals Can one not equally argue that size is not a real property because what one of us can hardly discern will appear as a huge mountain to some minute animal (BPW, 152)? If we argue that neither heat nor cold is in water, because it can seem warm to one hand and cold to another, we can just as well argue that there are no real sizes or shapes in the world, because what looks large and angular to a nearby eye looks small and round to a distant eye (BPW, 153) At the end of the Wrst dialogue, Hylas, accepting that material objects are in themselves imperceptible, still maintains that they are perceived through our ideas But Philonous mocks this: how can a real thing, in itself invisible, be like a colour? Hylas has to concur that nothing but an idea can be like an idea, and that no idea can exist without the mind; hence he is unable to defend the claim that ideas give us any information about anything outside the mind In the next chapter we will follow the course of the argument in the second and third dialogues in which Berkeley seeks to establish his metaphysical immaterialism But to complete our account of his epistemology we have to consider what he has to say not only about the ideas of the senses, but also about the universal ideas that have traditionally been regarded as the province of the intellect Locke had said that the ability to form general ideas was the most important diVerence between humans and dumb animals Unlike animals, humans use language; and the words of language have meaning by standing for ideas, and general words, such as sortal predicates, correspond to abstract general ideas In his Principles of Human Knowledge Berkeley mounted a destructive attack on Locke’s theory of abstraction Abstract ideas are said to be attained in the following manner: 148