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a definite molecular condition of motion or structure is set
up in the brain; or who would be disposed even to deny
that if the motion or structure be induced by internal
causes instead of external, the effect on consciousness will
be the same ? Let any nerve, for example, be thrown by
morbid action into the precise state of motion which would
be communicated to it by the pulses of a heated body,
surely that nerve will declare itself hot—the mind will
accept the subjective intimation exactly as if it were ob-
jective. The retina may be excited by purely mechanical
means. A blow on the eye causes a luminous flash, and
the mere pressure of the finger on the external ball pro-
duces a Star Of light, which Newton compared to the circles
on a peacock’s tail. Disease makes pe0ple see visions and
dream dreams; but, in all such cases, could we examine
the organs implicated, we should, on philos0phical grounds,
expect to find them in that precise molecular condition
which the real objects, if present, would superinduce.

The relation of physics to consciousness being thus
invariable, it follows that, given the state of the brain, the
corresponding thought or feeling might be inferred; or
given the thought or feeling, the corresponding state of the
brain might be inferred. But how inferred ? It would be
at bottom not a case of logical inference at all, but of
empirical association. You may reply that many of the
inferences of science are of this character; the inference,
for example, that an electric current of a given direction
will deflect a magnetic needle in a definite way; but the
cases differ in this, that the passage from the current to the
needle, if not demonstrable, is thinkable, and that we enter-
tain no doubt as to the final mechanical solution of the
problem. But the passage from the physics of the brain
to the corresponding facts of consciousness is unthinkable.
Granted that a definite thought, and a definite molecular
action in the brain occur simultaneously; we do not possess

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