20 Philosophical Introduction

entertaining?’ and the question ‘Which functional state is your mind in
when you entertain it?’ are required to get the same answer.
Frege’s structural problem is that, though he wants to be an externalist
about MOPs, the architecture of his theory won’t let him.14 Frege’s reason
for wanting to be an externalist about MOPs is that he thinks, quite
wrongly, that if MOPs are mental then concepts won’t turn out to be
public. But if MOPs aren’t mental, what kind of thing could they be such
that necessarily for each MOP there is only one way in which a mind can
entertain it? (And/or: what kind of mental state could entertaining a MOP
be such that necessarily there is only one way to entertain each MOP?) As
far as I can tell, Frege’s story offers nothing at all to scratch this itch with.
If, however, MOPS are in the head,15 then they can be proximal mental
causes and are, to that extent, apt for functional individuation. If MOPs
are both in the head and functionally individuated, then a MOP’s identity
can be constituted by what happens when you entertain it.16 And if the
identity of a MOP is constituted by what happens when you entertain it,
then of course there is only one way to entertain each MOP. In point of
metaphysical necessity, the alleged ‘different ways of entertaining a MOP’
would really be ways of entertaining different MOPs.
The moral, to repeat, is that even Frege can’t have 5.3 if he holds onto
5.1. Even Frege should have been a mentalist about MOPs if he wished to
remain in other respects a Fregean. On the other hand (perhaps this goes
without saying), to claim that MOPs must be mental objects is quite
compatible with also claiming that they are abstract objects, and that
abstract objects are not mental. The apparent tension is reconciled by
taking MOPS-qua-things-in-the-head to be the tokens of which MOPSqua-
abstract-objects are the types. It seems that Frege thought that if
meanings can be shared it somehow follows that they can’t also be
20 Philosophical Introduction
14 In this usage, an ‘externalist’ is somebody who says that ‘entertaining’ relates a
creature to something mind-independent, so Frege’s externalism is entailed by his Platonism.
Contrast the prima facie quite different Putnam/Kripke notion, in which an externalist is
somebody who says that what you are thinking depends on what world you’re in. (Cf. Preti
1992, where the distinction between these notions of externalism is sorted out, and some of
the relations between them are explored.)
15 This way of talking is, of course, entirely compatible with the current fashions in
Individualism, Twins, and the like. Twins are supposed to show that referents can distinguish
concepts whose causal roles are the same. For the demonstration to work, however, you’ve
got to assume that Twins ipso facto have the causal roles of their concepts in common; viz.
that whatever contents may supervene on, what causal roles supervene on is inside the head.
That’s precisely what I’m supposing in the text.
16 Notice that this is not to say that concepts are individuated by the mental processes
they cause, since a concept is a MOP together with a content; and I’ve taken an
informational view of the individuation of contents. It’s thus open to my version of RTM
that ‘Twin-Earth’ cases involve concepts with different contents but the same MOPs.
The Background Theory 21
particulars. But it beats me why he thought so. You might as well argue
from ‘being a vertebrate is a universal’ to ‘spines aren’t things’.
We’re almost through with this, but I do want to tell you about an
illuminating remark that Ernie Sosa once made to me. I had mentioned to
Ernie that I was worried about why, though there are lots of ways to grasp
a referent, there’s only one way to grasp a MOP. He proceeded to poohpooh
my worry along the following lines. “Look,” he said, “it’s pretty clear
that there is only one way to instantiate a property, viz. by having it. It
couldn’t be, for example, that the property red is instantiated sometimes by
a thing’s being red and sometimes by a thing’s being green. I don’t suppose
that worries you much?” (I agreed that it hadn’t been losing me sleep.)
“Well,” he continued, with a subtle smile, “if you aren’t worried about there
being only one way to instantiate a property, why are you worried about there
being only one way to grasp a mode of presentation?”
I think that’s very clever, but I don’t think it will do. The difference is
this: It is surely plausible on the face of it that ‘instantiating property P’
is just being P; being red is all that there is to instantiating redness. But
MOP is a technical notion in want of a metaphysics. If, as seems likely, the
identity of a mental state turns on its causal role, then if MOPs are to
individuate mental states they will have to be the sorts of things that the
causal role of a mental state can turn on. But it’s a mystery how a MOP
could be that sort of thing if MOPs aren’t in the head. If (to put the point
a little differently) their non-mental objects can’t distinguish thoughts, how
can MOPS distinguish thoughts if they are non-mental too? It’s as though
the arithmetic difference between 3 and 4 could somehow explain the
psychological difference between thinking about 3 and thinking about 4.
That red things are what instantiate redness is a truism, so you can have
it for free. But Frege can’t have it for free that, although same denotation
doesn’t mean same mental state, same MOP does. That must depend on
some pretty deep difference between the object of thought and its vehicle.
Offhand, the only difference I can think of that would do the job is
ontological; it requires MOPs to be individuated by their roles as causes
and effects of mental states, and hence to themselves be mental. So I think
we should worry about why there’s only one way to grasp a MOP even
though I quite agree that we shouldn’t worry about why there’s only one
way to instantiate a property.
Well, then, that’s pretty much it for the background theory. All that
remains is to add that in for a penny, in for a pound; having gone as far as
we have, we might as well explicitly assume that MOPs are mental
representations. That, surely, is the natural thing to say if you’re supposing,
on the one hand, that MOPs are among the proximal determinants of
mental processes (as per Thesis Five) and that mental processes are
computations on structured mental representations (as per Thesis Two).
It’s really the basic idea of RTM that Turing’s story about the nature of
mental processes provides the very candidates for MOP-hood that Frege’s
story about the individuation of mental states independently requires. If
that’s true, it’s about the nicest thing that ever happened to cognitive
science.
So I shall assume that it is true. From here on, I’ll take for granted that
wherever mental states with the same satisfaction conditions have different
intentional objects (like, for example, wanting to swallow the Morning
Star and wanting to swallow the Evening Star) there must be
corresponding differences among the mental representations that get
tokened in the course of having them.
Now, finally, we’re ready to get down to work. I’m interested in such
questions as: ‘What is the structure of the concept DOG?’ Given RTM as
the background theory, this is equivalent to the question: ‘What is the
MOP in virtue of entertaining which thoughts have dogs as their
intentional objects?’ And this is in turn equivalent to the question: ‘What
is the structure of the mental representation DOG?’
And my answer will be that, on the evidence available, it’s reasonable to
suppose that such mental representations have no structure; it’s reasonable
to suppose that they are atoms.