TRANSACTIONS OF THE SECTIONS. 5 
as the heat of a fire, being produced by the same chemical process. Animal mo- 
tion, too, is as directly derived from the food of the animal, as the motion of 
Trevethyck’s walking-engine from the fuel in its furnace. As regards matter, the 
animal body creates nothing; as regards force, it creates nothing. Which of you 
by taking thought can add one cubit to his stature? All that has been said regard- 
ing the plant may be restated with regard to the animal. Every particle that 
enters into the composition of a muscle, a nerve, or a bone, has been placed in its 
osition by molecular force. And unless the existence of law in these matters be 
enied, and the element of caprice introduced, we must conclude that, given the 
relation of any molecule of the body to its environment, its position in the body 
might be predicted. Our difficulty is not with the guality of the problem, but with 
its complexity; and this difficulty might be met by the simple expansion of the 
faculties which man now possesses. Given this expansion, and given the necessary 
molecular data, and the chick might be deduced as rigorously and as logically from 
the egg as the existence of Neptune was deduced from the disturbances of Uranus, 
or as conical refraction was deduced from the undulatory theory of light. 
You seeI am not mincing matters, but avowing nakedly what many scientific 
thinkers more or less distinctly believe. The formation of a crystal, a plant, or an 
animal, is in their eyesa purely mechanical problem, which differs from the pro- 
blems of ordinary mechanics in the smallness of the masses and the complexity of 
the processes involved. Here you have one half of our dual truth ; let us now glance 
at the other half. Associated with this wonderful mechanism of the animal body 
we have phenomena no less certain than those of physics, but between which and 
the mechanism we discern no necessary connexion. A man, 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 ponder it is the brain that thinks, when our passions or 
affections are excited it is through the instrumentality of the brain. Let us 
endeavour to be a little more precise here. [ hardly imagine that any profound 
scientific thinker, who has reflected upon the subject, exists who would not 
admit the extreme probability of the hypothesis, that for every fact of conscious- 
ness, whether in the domain of sense, of thought, or of emotion, a certain definite 
molecular condition is set up in the brain; that this relation of physics to con- 
sciousness is invariable, so that, given the state of the brain, the corresponding 
thought or feeling might be inferred; or given the thought or feeling, the corre- 
sponding state of the brain might be inferred. But how inferred? It is 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 entertain 
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 the intellectual organ, nor apparently any rudi- 
ment of the organ, which would enable us to pass by a process of reasoning from 
the one phenomenon to the other. They appear together, but we do not know 
why. Were our minds and senses so expanded, strengthened, and illuminated as 
to enable us to see and feel the very molecules of the brain; were we capable of 
following all their motions, all their groupings, all their electric discharges, if such 
there be; and were we intimately acquainted with the corresponding states of 
thought and feeling, we should be as far as ever from the solution of the problem, 
“ How are these physical processes connected with the facts of consciousness ?” 
The chasm between the two classes of phenomena would still remain intellectually 
impassable. Let the consciousness of Jove, for example, be associated with a right- 
handed spiral motion of the molecules of the brain, and the consciousness of hate 
with a left-handed spiral motion. We should then know when we love that the 
motion is in one direction, and when we hate that the motion is in the other; but 
the “ wy?” would still remain unanswered. 
In affirming that the growth of the body is mechanical, and that thought, as 
