Throughout the text, fundamental questions concerning the nature of visual perception are addressed.

In this paper I address an important question concerning the nature of visual content: are the contents of human visual states and experiences exhaustively fixed or determined (in the non-causal sense) by our intrinsic physical properties? The individualist answers this question affirmatively. I will argue that such an answer is mistaken. A common anti-individualist or externalist tactic is to attempt to construct a twin scenario involving humanoid duplicates who are embedded in environments that diverge in such a way that it (...) appears to be necessary to attribute divergent contents to their respective visual states. In the first half of the paper I discuss some of the twin scenarios that are prominent in the literature and argue that they fail to undermine individualism. Indeed I argue that due to important facts about our internal workings, a convincing externalist twin scenario involving humanoid protagonists cannot be constructed. However, I argue that such a result does not conclusively establish an individualist thesis and that in order to settle the question at issue it is necessary to construct an independently motivated theory of visual content. I attempt to do this in the second half of the paper by developing a theory at the core of which is the idea that the contents of our visual states and experiences are determined by the causal powers vis-. (shrink)

David Marr's theory of vision has been widely cited by philosophers and psychologists. I have three projects in this paper. First, I try to offer a perspicuous characterization of Marr's theory. Next, I consider the implications of Marr's work for some currently popular philosophies of psychology, specifically, the "hegemony of neurophysiology view", the theories of Jerry Fodor, Daniel Dennett, and Stephen Stich, and the view that perception is permeated by belief. In the last section, I consider what the phenomenon of (...) vision must be like for Marr's project to succeed. (shrink)

According to Marr's theory of vision, computational processes of early vision rely for their success on certain "natural constraints" in the physical environment. I examine the implications of this feature of Marr's theory for the question whether psychological states supervene on neural states. It is reasonable to hold that Marr's theory is nonindividualistic in that, given the role of natural constraints, distinct computational theories of the same neural processes may be justified in different environments. But to avoid trivializing computational explanations, (...) theories must respect methodological solipsism in the sense that within a theory there cannot be differences in content without a corresponding difference in neural states. (shrink)

Many philosophers and psychologists who approach the issue of representation from a computational or measurement theoretical perspective end up having to deny the possibility of junk representations?representations present in an organism's head but that enter into no psychological processes or produce no behaviour. However, I argue, a more functional perspective makes the possibility of junk representations intuitively quite plausible?so much so that we may wish to question those views of representation that preclude the possibility of junk representations. I explore some (...) of the reasons we should care about the possibility of junk representations and conclude with some speculation about whether junk representations are in fact present in our heads. (shrink)

Frances Egan argues that the states of computational theories of vision are individuated individualistically and, as far as the theory is concerned, are not intentional. Her argument depends on equating the goals and explanatory strategies of computational psychology with those of its algorithmic level. However, closer inspection of computational psychology reveals that the computational level plays an essential role in explaining visual processes and that explanations at this level are nonindividualistic and intentional. In conclusion, I sketch an account of content (...) in which content does the sort of explanatory work that Egan denies is possible. (shrink)

Noam Chomsky and Frances Egan argue that David Marr.

An important class of teleological theories cannot explain the representational content of visual states because they fail to address the relationship between the world, projected retinal stimuli, and perception. A different approach for achieving a naturalized theory of visual content is offered that rejects the traditional internalism/externalism debate in favor of what is termed “empirical externalism.” This position maintains that, while teleological considerations can underwrite a broad understanding of representation, the content of visual representation can only be determined empirically according (...) to accumulated past experience. A corollary is that a longstanding problem concerning the indeterminacy of visual content is dissolved. (shrink)