406 FRAGMENTS OF SCIENCE. 
for example, can say " I feel," "I think," " I love;" but 
how does consciousness infuse itself into the problem? 
The human brain is said to be the organ of thought and 
feeling: when we are hurt, the brain feels it; when we pon- 
der, or when our passions or affections are excited, it is 
through the instrumentality of the brain. Let us endeavor 
to be a little more precise here. I hardly imagine there 
exists a profound scientific thinker, who has reflected upon 
the subject, unwilling to admit the extreme probability of 
the hypothesis, that for every fact of consciousness, 
whether in the domain of sense, thought, or emotion, 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 produces 
a star of light, which Newton compared to the circles on 
a peacock's tail. Disease makes people see visions and 
dream dreams; but, in all such cases, could we examine 
the organs implicated, we should, on philosophical 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 in- 
variable, 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 conceivable, aud that 
we entertain no doubt as to the final mechanical solution 
pf the problem. But the passage from the physics of the 
