Keith Allen

What, according to Locke, are ideas? I argue that Locke does not give an account of the nature of ideas. In the Essay, the question is simply set to one side, as recommended by the “Historical, plain Method” that Locke employs. This is exemplified by his characterization of ‘ideas’ in E I.i.8, and the discussion of the inverted spectrum hypothesis in E II.xxxii. In this respect, Locke's attitude towards the nature of ideas in the Essay is reminiscent of Boyle's diffident attitude towards the nature of matter. In posthumously published work, however, Locke suggests that the enquiry into the nature of ideas is one of the things that the enquiry into the extent of human knowledge undertaken in the Essay actually shows to lie beyond the “compass of human understanding”. In this respect, Locke's attitude towards the nature of ideas is reminiscent of Sydenham's attitude towards the nature of diseases.

What is the relationship between being coloured and looking coloured? According to Alva Noë, to be coloured is to manifest a pattern of apparent colours as the perceptual conditions vary. I argue that Noë’s ‘phenomenal objectivism’ faces similar objections to attempts by traditional dispositionalist theories of colour to account for being coloured in terms of looking coloured. Instead, I suggest that to be coloured is to look coloured in a ‘non-perspectival’ sense, where non-perspectival looks transcend specific perceptual conditions.

It is widely held by philosophers not only that there is a causal condition on perception but also that the causal condition is a conceptual truth about perception. One influential line of argument for this claim is based on intuitive responses to a style of thought experiment popularized by Grice. Given the significance of these thought experiments to the literature, it is important to see whether the folk in fact respond to these cases in the way that philosophers assume they should. We test folk intuitions regarding the causal theory of perception by asking our participants to what extent they agree that they would ‘see’ an object in various Gricean scenarios. We find that the intuitions of the folk do not strongly support the causal condition; they at most strongly support a ‘no blocker’ condition. We argue that this is problematic for the claim that the causal condition is a conceptual truth.

According to naïve realist (or primitivist) theories of colour, colours are sui generis mind-independent properties. The question that I consider in this paper is the relationship of naïve realism to what Mark Johnston calls Revelation, the thesis that the essential nature of colour is fully revealed in a standard visual experience. In the first part of the paper, I argue that if naïve realism is true, then Revelation is false. In the second part of the paper, I defend naïve realism against a number of objections.

What are hallucinations? A common view in the philosophical literature is that hallucinations are degenerate kinds of perceptual experience. I argue instead that hallucinations are degenerate kinds of sensory imagination. As well as providing a good account of many actual cases of hallucination, the view that hallucination is a kind of imagination represents a promising account of hallucination from the perspective of a disjunctivist theory of perception like naïve realism. This is because it provides a way of giving a positive characterisation of hallucination—rather than characterising hallucinations in negative, relational, terms as mental events that are subjectively indistinguishable from veridical perceptual experiences.

Variations in colour perception have featured prominently in recent attempts to argue against the view that colours are objective mind-independent properties of the perceptual environment. My aim in this paper is to defend the view that colours are mind-independent properties in response to worries arising from one type of empirically documented case of perceptual variation: variation in the perception of the «unique hues». §1 sets out the challenge raised by variation in the perception of the unique hues. I argue in §2 that the empirical findings are less dramatic than they might initially appear, and in §3 that accounting for the inter-personal differences is consistent with the view that colours are mind-independent properties that normal subjects veridically perceive, at least roughly speaking.

Ralph Cudworth (1617–1688) is a member of the group of philosophers and theologians commonly called ‘the Cambridge Platonists’. Although not part of the canon of great early modern philosophers, Cudworth’s work is of more than merely passing interest. Cudworth was an influential philosopher in the early modern period both for his criticisms of contemporaries like Hobbes, Descartes, and Spinoza, and for his own distinctive philosophical views. This entry focusses on Cudworth’s views on mind and body, considering both his criticisms of contemporaries’ theories of mind and body, and outlining his alternative form of dualism in which plastic nature plays a central role.