A letter, so long as it is connected with one set of nerves, is one
thing; loose it from connection with those nerves—open your fingers and
drop it in the opening of a pillar box—and it becomes part and parcel of
another nervous system. Letters in transitu contain all manner of varied
stimuli and shocks, yet to the postman, who is the nerve that conveys
them, they are all alike, except as regards mere size and weight. I
should think, therefore, that our nerves and ganglia really see no
difference in the stimuli that they convey.
And yet the postman does see some difference: he knows a business letter
from a valentine at a glance and practice teaches him to know much else
which escapes ourselves. Who, then, shall say what the nerves and
ganglia know and what they do not know? True, to us, as we think of a
piece of brain inside our own heads, it seems as absurd to consider that
it knows anything at all as it seems to consider that a hen’s egg knows
anything; but then if the brain could see us, perhaps the brain might say
it was absurd to suppose that that thing could know this or that.
Besides what is the self of which we say that we are self-conscious? No
one can say what it is that we are conscious of. This is one of the
things which lie altogether outside the sphere of words.
The postman can open a letter if he likes and know all about the message
he is conveying, but, if he does this, he is diseased _qua_ postman. So,
maybe, a nerve might open a stimulus or a shock on the way sometimes, but
it would not be a good nerve.