*1 would like to thank the following, for many helpful comments, criticisms and/or discussions: Mike Antony, Ned Block, George Boolos, Tyler Burge, Noam Chomsky, Ellery Eells, Malcolm Forster, David Kirsh, Jay Lebed, Sarah Patterson, Paul Pietroski, Elliot Sober and an anonymous reviewer. Thanks also to Ellen Hildreth, of the M.I.T. Vision Laboratory, for information about the computational theory of vision, and help with Marr exegesis. And thanks especially to Rob Cummins for his most generous help with the preparation of this paper. 'Burge, T., Individualism and Psychology, The Philosophical Review 95 (1986), pp. 3-45. 21 shall follow Burge in referring to it as Marr's theory. As Burge notes, very substantial contributions have been made to the computational theory by various others. The most complete and accessible account of the theory is to be found in Marr's book (Vision, San Francisco, Calif.: W. H. Freeman and Co., 1982). All references to Marr are from the book, unless otherwise specified. 3By content I intend something that is individuated by its semantic or intentional properties. Two identical syntactic tokens may have different representational contents. A representation is a syntactic object, though typically it will have semantic properties.