To facilitate discussion, I will follow Paul Humphreys in numbering my comments.
1. Our starter paper contains a number of interesting and plausible ideas about how electronic communication will change the shape of philosophical activities and the philosophical enterprise generally. We are, of course, currently engaged in a bit of ``electronic philosophy,'' and the extent to which this kind of philosophical activity grows will be largely determined, I suspect, by its degree of fruitfulness. There seems to be good reason to believe that collaborative ventures such as this will be a step forward for philosophy.
2. E-mail, however, makes use of linguistic or propositional representations, and so does not constitute a radically new style of representation in electronic philosophy, despite the changes it will effect in the speed of - and participation in - philosophical discussions. The regular use of graphical images, on the other hand, would constitute a new medium or vehicle for philosophy, and so I would like to focus my remarks on the extent to which graphical images and other non-propositional representations might help philosophers ``escape from the propositional prison.'' Paul Humphreys' suggestion in section (8) is that philosophical work - in particular, the conveying of (philosophical?) information - has been (is, will be) hindered by restriction to the propositional format.
3. We should first note that in section (6) of the starter paper, Humphreys remarks that he is suggesting a ``supplementation, rather than a wholesale replacement'' of the propositional approach to philosophy. The supplementations he explicitly mentions are of two kinds. First, there are the graphical representations of quantitative data from other areas - physics, evolutionary theory, etc. If philosophers are to continue to effectively theorise about these areas, they will need to incorporate these representations into their own work. Second, there are the visual and auditory representations from other areas, in particular, the fine arts. As Humphreys suggests, these may serve as examples of theses in aesthetics, and as such they will enhance the quality and effectiveness of work in that area. In both cases, these supplementary non-propositional representations can be transmitted electronically.
4. This brings us to the question of whether philosophical ideas and theses per se are amenable to non-propositional representation. Is the ``fixation on propositional representations'' by philosophers (section 11) actually a fixation, or more of a necessity? While we have before us clear examples of how scientific and everyday information can be represented visually/pictorially, it is not yet clear that the more abstract information that philosophers typically deal in admits of such representation. In the scientific examples, it is clear how quantitative information can be graphically displayed, and it is clear why and how these displays are helpful. But even in the everyday examples, pictures often need to be accompanied by symbols. Consider the very simple information that smoking is prohibited in the area. This is typically and effectively conveyed pictorially by a picture of a cigarette that is enclosed in a circle that is diagonally bisected. Imagine how difficult it would be to pictorially convey the information that smoking is prohibited without the use of a diagonally bisected circle. Now, this symbol is not a proposition, but it is an abstraction from the world of tables, chairs, and cigarettes, and it is language-like in nature. Unlike a representational painting or picture, it does not admit of direct comparison to the fact it represents.
5. Humphreys is right to point out (section 13) that realistic graphical representations have the following advantage over claims made in natural languages: they can be compared directly to the sensory evidence available from the thing being imaged. But consider some paradigms of objects of philosophical theorising: goodness, knowledge, universals, meanings, and the like. These are all abstract in some sense. It's hard to see how we could adequately represent our ideas about these matters pictorially or in some other non-propositional format.
6. Humphreys is also right to suggest (section 14) that the propositional orientation in philosophy may be responsible for the (what seems to many of us) increasingly inappropriate use of ``language of thought'' architectures to model certain cognitive capacities (e.g. pattern recognition). But his claim that ``We do often literally just see that something is the case'' needs to be clarified. It sounds like the claim of a direct realist who dispenses with (mental) representations altogether. Now, direct realism may be true, and connectionism may be a way of seeing how it is true, but it is unclear how this advances a thesis about representation, except that it suggests that the language of thought hypothesis may be wrong for certain cognitive abilities (but in this case it would be wrong because representationalism about this ability is wrong).
7. Let's go a step further and assume that some form of connectionism is right, and further, that thought generally is non-propositional or nonlinguistic in character (i.e., our minds are not virtual symbol systems implemented in a connectionist network). Still, it seems that in order to express our thoughts - especially our philosophical thoughts - we need to use the written or spoken word. Surely some of our thoughts get expressed in our nonverbal actions, in drawings, etc. But to reiterate a point made earlier, it seems hard to imagine how a more abstract or sophisticated thought might be adequately conveyed non-propositionally. (Could a nonverbal associative train of images do the work?)
8. So with regard to Humphreys' section (14), we should ask: (a) how many of our philosophical representations are non-propositional?, and (b) could this non-propositional style of representation be exploited electronically to philosophical ends?
My suspicion is that although some thoughts appear to be non-propositional (e.g., you can think about your last vacation by forming a mental image of yourself on a beach), typical philosophical thoughts are linguistic or propositional in some sense (and to the extent that we could not entertain these thoughts without having a complex language.)
9. We should view both Humphreys' paper and my comments as a challenge to say just how non-propositional representations might be used to liberate or otherwise enhance work outside of the examples in philosophy of science and aesthetics. In philosophy of cognitive science philosophers can use (and may eventually be forced to use) computer simulations of abstract neural nets as models of belief and other mental phenomena. This may eventually become the norm in philosophy of mind. Could these practices be extended to epistemology, or metaphysics, or ethics?