Abstract

The project in this essay will be to chart a naturalist theory of content for perceptual states, where the content is constituted by that state of the world picked out by a proposition telling us what it is that is believed, desired, etc. We will focus on the perceptual states of desire and vision, and only on contents involving physical objects. ;We will begin by doing an overview of some recent attempts to define function. We will consider a treatment by Peter Godfrey-Smith, who looks at the "recent history" of an organism to determine the functions of its parts. We will end the section with a definition of function upon which we will base what follows. ;Then we investigate the nature of need, in order to get an eventual handle on desire. Desire states function to dispose behavior that fulfills unmet needs. We will pick out the state change which meets the need and extinguishes the desire as the proper object of the desire state D in question. ;Then we turn to the problems of determining content in visual states. We will look for how the visual system provides information which allows an organism to locate and re-locate an object in space over time. We will use David Marr's theory of vision as a basis for understanding the function of the visual system. We will pay particular attention to how the visual sytem's modules transform two-dimensional information into information about the relative depths and locations of objects in the world. ;Finally, material from Gareth Evans will help us investigate the role of the behavioral system in determining the content of perceptual states. What makes Marr's information information "about" depth and placement depends crucially upon how it is used in patterns of behavior to enhance fitness. This gives us a method of cashing out what it is to locate and re-locate an object without relying on an unexplained ability to represent