The Origin of Ideas
Where do our ideas come from? What gives ideas their content? There is an old and natural story about this: call it the “exemplar theory”. Consider the idea of blue (the concept blue, the meaning of “blue”): it arises in the mind by virtue of perceptual contact with exemplary blue things—this contact with exemplars gives it the intentional content it has. We have an idea of a particular sensible quality, which objects can instantiate, and the idea has that content because of its origin in instances of the quality that are perceived by the subject. To be more explicit: the idea refers to a specific universal, viz. the color blue, and it does so as the product of two other relations—instantiation and perception. Particular objects instantiate the universal and then perceiving subjects encounter those instances and derive the concept from them. In some versions the derivation works by simple causation, as the perceived quality causes sensory experiences with the corresponding content; in other versions it is deemed necessary for the subject to perform an operation of abstraction on the perceived instance—the universal is abstracted from the encountered particular. The essential point, however, is that the mind apprehends the universal by way of responding to instances of it in the perceived environment: this process is what mediates the referential link between mind and universal. We come to form an idea of a sensible quality like blue because we interact through our senses with the extension of that quality—with external objects that exemplify it. The exemplar establishes the idea in our mind.
We can think of the exemplar theory as an account of emergence that offers a kind of reduction. Intentionality emerges from a basis in perception of instances: the mind grasps the universal by encountering instances of it—the grasping supervenes on the encountering. Alternatively, the apprehension of universals reduces to the Read more
 Locke introduces the notion of abstraction in chapter XI, section 9, of An Essay Concerning Human Understanding (London: Penguin Books, 1997), ed. Roger Woolhouse (followed by the charmingly named section “Brutes Abstract Not”). Earlier he states his basic thesis thus: “First, our senses, conversant about particular sensible objects, doconvey into the mind, several distinct perceptions of things, according to those various ways, wherein those objects do affect them: and thus we come by those ideas, we have ofyellow, white, heat, cold, soft, hard, bitter, sweet, and all those which we call sensible qualities, which when I say the senses convey into the mind, I mean, they from external objects convey into the mind what produces there those perceptions.” 109-10. Notice here the emphasis on external objects: the senses convey the qualities of objects outside of us into the mind—they don’t just present subjective impressions quite distinct from such objects. Just as I think about external objects by perceiving them, so I think about their qualities by perceiving them. I venture to suggest that this is not just a broad philosophical tradition, associated with empiricism, but also the view of common sense: it just seemsobvious that we derive our ideas of the qualities of things by perceiving those qualities inthings. So if this view proves false, a chunk of common sense collapses.