there is encapsulation to the extent that modules are unable to make use of
anything other than their own proprietary sources of information.
Limited access to the representations processed within input systems is
taken by Fodor to be evidenced by the extent to which such represen-
tations fail to be available for conscious report. He suggests that the
general rule is that only theWnal results of input processing are completely
available to central cognition. So if we think of input processing as a richly
mediated channelling in which information isWltered inwards from the
sensory transducers, representations close to the sensory transducers will
be completely inaccessible to the conscious mind. And for sure, we are not
able to pronounce on the images formed at our retinas or the patterns of
Wring across our rods and cones. Moreover, both casual reXection and
empirical investigation show that many informational details which must
be represented at some level in the process of perception either do not
consciously register at all or else are almost immediately forgotten. Thus
one can tell the time without noticing details of the clock’s dial or the
watch’s face; one can read words on a page without being able to say how
some of the characters that composed them were shaped, or even how
some of the words were spelled; and one can extract and remember the
message which someone gave you while forgetting the exact words in
which it was put.
The other aspect of the insulation of Fodorian modules, namely their
informational encapsulation, is intimately connected with the dividing line
Fodor draws between input-systems and central cognition. Central cog-
nitive processes, for Fodor, are those which control such activities as
decision-making, making up your mind about what beliefs to hold, and
theorising. Fodor supposes that in order to work rationally such central
systems must be capable of integrating all of the information available to a
subject, in order to make the best decision considering all the circumstan-
ces, and to form the most reasonable belief on the balance of all the
evidence. By contrast, the modular input-systems are blinkered and simply
incapable of taking any account of other things which the subject may be
well aware of.
The persistence of perceptual illusions provides Fodor with a striking
illustration of his encapsulation claim. Consider, for example, the well-
known Mu ̈ller-Lyer illusion as displayed inWgure 3.2. You must have seen
this sort of thing before, and you would bet that the two horizontal lines
are really of equal length. Perhaps you have even satisWed yourself of this
by measuring them oVwith a ruler. But what you know about their relative
length is quite impotent to alleviate the illusion – the line at the bottom still
goes on looking longer than the line above, even though you are absolutely
sure that it is not.
Fodorian modularity 63