The Background Theory 11

Addendum: if computation is just causation that preserves semantic
values, then the thesis that thought is computation requires of mental
representations only that they have semantic values and causal powers
that preserve them. I now add a further constraint: many mental
representations have constituent ( part/whole) structure, and many mental
processes are sensitive to the constituent structure of the mental
representations they apply to. So, for example, the mental representation
that typically gets tokened when you think . . . brown cow . . . has, among
its constituent parts, the mental representation that typically gets tokened
when you think . . . brown . . .; and the computations that RTM says get
performed in processes like inferring from . . . brown cow . . . to . . .
brown . . . exploit such part/whole relations. Notice that this is an
addendum (though it’s one that Turing’s account of computation was
designed to satisfy). It’s untendentious that RTM tolerates the possibility
of conceptual content without constituent structure since everybody who
thinks that there are mental representations at all thinks that at least some
of them are primitive.6
The aside I can’t resist is this: following Turing, I’ve introduced the
notion of computation by reference to such semantic notions as content
and representation; a computation is some kind of content-respecting
causal relation among symbols. However, this order of explication is OK
only if the notion of a symbol doesn’t itself presuppose the notion of a
computation. In particular, it’s OK only if you don’t need the notion of a
computation to explain what it is for something to have semantic
properties.We’ll see, almost immediately, that the account of the semantics
of mental representations that my version of RTM endorses, unlike the
account of thinking that it endorses, is indeed non-computational.
Suppose, however, it’s your metaphysical view that the semantic
properties of a mental representation depend, wholly or in part, upon the
computational relations that it enters into; hence that the notion of a
computation is prior to the notion of a symbol. You will then need some
other way of saying what it is for a causal relation among mental
representations to be a computation; some way that does not presuppose
such notions as symbol and content.7 It may be possible to find such a
notion of computation, but I don’t know where. (Certainly not in Turing,
The Background Theory 11
6 Connectionists are committed, willy-nilly, to all mental representations being
primitive; hence their well-known problems with systematicity, productivity, and the like.
More on this in Chapter 5.
7 Not, of course, that there is anything wrong with just allowing ‘symbol’ and
‘computation’ to be interdefined. But that option is not available to anyone who takes the
theory that thought is computation to be part of a naturalistic psychology; viz. part of a
programme of metaphysical reduction. As Turing certainly did; and as do I.
who simply takes it for granted that the expressions that computing
machines crunch are symbols; e.g. that they denote numbers, functions,
and the like.) The attempts I’ve seen invariably end up suggesting (or
proclaiming) that every causal process is a kind of computation, thereby
trivializing Turing’s nice idea that thought is.
So much for mental processes.
Fourth Thesis: Meaning is information (more or less).
There actually are, in the land I come from, philosophers who would agree
with the gist of RTM as I’ve set it forth so far. Thesis Four, however, is
viewed as divisive even in that company. I’m going to assume that what
bestows content on mental representations is something about their
causal-cum-nomological relations to the things that fall under them: for
example, what bestows upon a mental representation the content dog is
something about its tokenings being caused by dogs.
I don’t want to pursue, beyond this zero-order approximation, the
question just which causal-cum-nomological relations are content-making.
Those of you who have followed the literature on the metaphysics of
meaning that Fred Dretske’s book Knowledge and the Flow of Information
(1981) inspired will be aware that that question is (ahem!) mootish. But I
do want to emphasize one aspect of the identification of meaning with
information that is pretty widely agreed on and that impacts directly on
any proposal to amalgamate an informational semantics with RTM: if
meaning is information, then coreferential representations must be
synonyms.
Just how this works depends, of course, on what sort of causal-cumnomological
covariation content is and what sort of things you think
concepts represent (properties, actual objects, possible objects, or
whatever). Suppose, for example, that you run the kind of informational
semantics that says:
A representationR expresses the property P in virtue of its being a law
that things that are P cause tokenings of R (in, say, some still-to-bespecified
circumstances C).
And suppose, for the sake of the argument, that being water and being
H2O are (not merely coextensive but) the same property. It then follows
that if it’s a law that WATER tokens covary with water (in C) it’s also a law
that WATER tokens covary with H2O (in C). So a theory that says that
WATER means water in virtue of there being the first law is also required
to say that WATER means H2O in virtue of there being the second.
Parallel reasoning shows that H2O means water, hence that WATER and
H2O mean the same.
12 Philosophical Introduction
You may wonder why I want to burden my up to now relatively
uncontroversial version of RTM by adding a theory of meaning that has
this uninviting consequence; and how I could reasonably suppose that
you’ll be prepared to share the burden by granting me the addition. Both
questions are fair.
As to the first, suppose that coextension is not sufficient for synonymy
after all. Then there must be something else to having a concept with a
certain content than having a mental representation with the kind of
world-to-symbol causal connections that informational semantics talks
about. The question arises: what is this extra ingredient? There is, as
everybody knows, a standard answer; viz. that what concepts one has is
determined, at least in part, by what inferences one is prepared to draw or to
accept. If it is possible to have the concept WATER and not have the
concept H2O, that’s because it’s constitutive of having the latter, but not
constitutive of having the former, that you accept such inferences as
contains H2O ® contains H. It is, in short, received wisdom that content
may be constituted in part by informational relations, but that unless
coreference is sufficient for synonymy, it must also be constituted by
inferential relations. I’ll call any theory that says this sort of thing an
Inferential Role Semantics (IRS).
I don’t want content to be constituted, even in part, by inferential
relations. For one thing, as we just saw, I like Turing’s story that inference
(qua mental process) reduces to computation; i.e. to operations on symbols.
For fear of circularity, I can’t both tell a computational story about what
inference is and tell an inferential story about what content is. Prima facie,
at least, if I buy into Inferential Role Semantics, I undermine my theory
of thinking.
For a second thing, I am inclined to believe that an inferential role
semantics has holistic implications that are both unavoidable and
intolerable. A main reason I love RTM so much is that the computational
story about mental processes fits so nicely with the story that psychological
explanation is subsumption under intentional laws; viz. under laws that
apply to a mental state in virtue of its content. Since computation is
presumed to respect content, RTM can maybe provide the mechanism
whereby satisfying the antecedent of an intentional law necessitates the
satisfaction of its consequent (see Fodor 1994: ch. 1). But I think it’s pretty
clear that psychological explanation can’t be subsumption under
intentional laws if the metaphysics of intentionality is holistic. (See Fodor
and Lepore 1992.)
For a third thing, as previously noted, the main point of this book will
be to argue for an atomistic theory of concepts. I’m going to claim, to put
it very roughly, that satisfying the metaphysically necessary conditions for