Externalism and Marr's theory of vision

According to one brand of 'externalism', cognitive theories should individuate mental content 'widely'--that is, partly in terms of environmental features. David Marr's theory of vision is often cited in support of this view. Many philosophers (most notably, Tyler Burge) regard it as a prime example of a fruitful cognitive theory that widely individuates the representations it posits. I argue that, contrary to popular belief, Marr's theory does not presuppose an externalist view of mental content.