Schneider, Susan (unpublished). "
The Nature of Symbols in the Language of Thought."
Schneider addresses the important problem of how to individuate LOT symbols. There is no accepted or even fully worked out solution to this problem in the literature. She gives various interesting and original arguments to the effect that LOT symbols are individuated by “total” computational role. In her view, computational role is found by Ramsifying over narrow cognitive science laws. Finally, she gives some interesting responses to the objection that if symbols are individuated holistically by their total computational role, then symbols cannot be shared. One of her responses is that cognitive science also has broad intentional laws, which do not range over symbols but over broad contents, which are publicly shared. So at least those laws apply to all subjects even though symbols aren’t shared.
Although I am sympathetic to a lot of what she says, I have some concerns.
Concern 1. Her proposal requires a non-semantic notion of symbol, but her non-semantic notion of symbol doesn’t seem to be well grounded. (Many authors have argued that nothing can be a symbol in the relevant sense without being individuated at least in part by semantic properties.) At the beginning, she appeals to Haugeland’s account of computation in terms of automatic formal systems. Unfortunately, the only clear and rigorous explication of the notion of formal systems that we possess is in terms of computation, so Haugeland’s account is circular. I think referring to Haugeland’s work in this context is unhelpful. Later, she gives her own account in terms of Ramsification over narrow cognitive science laws. But this raises the question of how these narrow cognitive science laws are to be discovered, which becomes all the more pressing in light of her stated view, later in the paper, that there are two sets of cognitive science laws: the narrow ones and the broad ones (ranging over broad contents). If ordinary cognitive science laws range over broad contents, how are we to discover the narrow ones? By doing neuroscience? (At some point, Schneider briefly mentions the “neural code,” something that
in my understanding of these things, is not related to her issue.) Without at least a sketch of an account of how the narrow laws are to be found, I am unclear on how this proposal is supposed to work.
I think Concern 1 might be addressed by appealing to the non-semantic notion of computation that I have developed in some recent papers (
forthcoming in Phil Studies and
forthcoming in Australasian J. Phil).
Concern 2: Ramsification is popular among philosophers of mind but it is only a formal maneuver. It this view is going to have real bite as philosophy of cognitive science, Ramsification should be fleshed out in terms of some individuative strategy that actually plays a role in science.
I think Concern 2 might be addressed by appealing to functional explanation, or even better, mechanistic explanation. This is the way actual cognitive scientists go about individuating their explanantia. Schneider should be sympathetic to this move, since she appeals to functional explanation later in the paper. Notice that an appeal to mechanistic explanation is already part of my account of computational individuation, so that both Concerns 1 and 2 can be addressed by appealing to my account. The crucial observation, which is missing from her paper, is that symbols are components (or states of a component) of a computing mechanism. If you have a mechanistic explanation of a system, you thereby have access to individuation conditions for its components, including symbols (in the case of computing mechanisms).
Concern 3: Pending a resolution of Concerns 1 and 2, I would like to know more about what Schneider means by “total” computational role and especially, how it is possible to test hypotheses on whether something is a “total” computational role. If it includes all possible input conditions and internal states, it seems that total computational role can never be discovered. For how can we be sure that we have all the relevant data? Do we have to test the system under all relevant conditions? Is this even possible? Is it possible to know that we have succeeded?
I think Concern 3 might be addressed by appealing, once again, to functional explanation or better, mechanistic explanation. For as Schneider points out in various places in her own paper, mechanistic explanation gives you a way to individuate components and their activities (including, I say, symbols). Furthermore, in order to find a mechanistic explanation, you don’t need to study all possible computations. You can proceed piecemeal, component by component, operation by operation.
When you do the mechanistic explanation of a computing mechanism, you discover that total computational role supervenes on (what may be called) primitive computational role plus input and internal state conditions. So all you need to individuate a symbol is its primitive computational role, i.e. the way the symbol affects the computational architecture (components, their primitive computational operations, and their organization). So pending further explication of what Schneider means by “total”, in order to individuate the symbols, as far as I can tell you don’t need “total” computational role. (Notice that in her paper Schneider already states individuation conditions similar to the ones I suggest, under T2 and T4, but she immediately shifts from those to “total” computational role.) I think individuation in terms of primitive computational role would generate a notion of symbol that can be shared between subjects, provided that subjects share their basic computational architecture.
