   According to the theory of direct reference, the function of such linguistic devices as proper names, indexicals and demonstratives is to introduce a concrete individual or particular into the proposition and/or belief expressed. To use David Kaplan’s (1979, 387) revealing word, a concrete individual is “trapped” within a singular proposition. The theory of direct reference seems like a useful antidote against the Frege/Russell tendency to minimize the contribution of concrete particulars to the individuation of human singular thoughts. Three trends of thoughts in recent philosophy of  mind and language have built on the theory of direct reference. First,  many of the insights of the theory of direct reference have been extended from thoughts about concrete individuals to thoughts about natural kinds by Kripke (1972) and Putnam (1974). This extension plays a crucial role in the externalist view of intentional mental states (about which see  section 10). Secondly, neo-Fregeans have responded  to the challenge of the theory of direct reference by providing a  suitable notion of “object-dependent” or “de  re” sense (see Evans, 1982 and McDowell, 1984). (For a  response to Frege’s puzzle about how two distinct beliefs can be about the same object on behalf of the theory of direct reference, see Salmon, 1986). Thirdly, the metaphysical and epistemological underpinnings of singular thoughts (and singular propositions) have given rise to a rich discussion of the contrast between two broad perspectives: descriptivism and singularism. According to descriptivism, we can only think about objects by thinking about the properties which they instantiate. But according to singularism, not all thoughts about objects are mediated by thoughts about their properties. For further discussion, see the papers collected in Jeshion (ed.) (2010), in particular Recanati (2010). 