say that the thought, ‘I am cold’ has the same sense (the same narrow
content) for each one of us. But those senses areaboutdiVerent things, and
diVerent tokens of the very same (narrow) thought can have diVerent
worldly truth-conditions. Defenders of wide, or ‘externalist’, content take
the second option. They say that since the token thoughts expressed by ‘I
am cold’ have diVerent truth-conditions in the case of each one of us (and
can in some cases be true while in other cases being false), those thoughts
belong to diVerent types, with diVerent contents. So we do not think the
same thing when we each of us think ‘I am cold’. The thoughts are distinct
because the referents are.
2 Arguments for wide contentIn this section of the chapter we shall consider some of the arguments
which have been oVered in defence of wide content, concluding with the
argument that narrow content is actually incoherent. Then in section 3 we
respond to this challenge, arguing that it is at leastpossiblethat psychology
should be narrow; and in section 4 we shall argue that explanatory psy-
chologyisnarrow.
2.1 Externalist intuitionsPutnam (1975a) devised a new type of philosophical thought-experiment
to demonstrate that meanings ‘ain’t in the head’. We are to imagine that
there is, or could be, an exact duplicate of Earth (Twin Earth, often written
‘Twearth’), where everything is exactly as it is on Earth, except for some
minor respect which can be varied depending upon the type of example.
Imagine, in particular, that everything on Twearth is exactly as it is on
Earth, down to the smallest detail,exceptthat on Twearth waterDH 2 O.
Rather, on Twearth water = XYZ, where the two substances can only be
distinguished from one another in a chemistry laboratory. Putnam argues
that if a person on Earth, Petere, asserts ‘Water is wet’ and his twin on
Twearth Petertwmakes the same utterance, then their thoughts diVer in
content (and their sentences diVer in meaning) because the substances they
respectively refer to are diVerent.
Suppose that neither Peterenor Petertwinitially knows the composition
of water/twater. Then each of them is told in similar circumstances ‘Water
is H 2 O’, and believes it. Surely, Putnam argues, they cannot have formed
the very samebelief, since Petere’s belief istruewhile Petertw’s belief isfalse.
And how can the very same thought-content be both true and false at one
and the same time? Yet every aspect of their brains and of their internal
(non-relationally described) psychology is, by hypothesis, exactly the
Arguments for wide content 133