this question. But man is not all intellect. If he were so, science
would, I believe, be his proper nutriment. But he feels as well as
thinks; he is receptive of the sublime and beautiful as well as of the
true. Indeed, I believe that even the intellectual action of a
complete man is, consciously or unconsciously, sustained by an
undercurrent of the emotions. It is vain to attempt to separate the
moral and emotional from the intellectual. Let a man but observe
himself, and he will, if I mistake not, find that in nine cases out of
ten, the emotions constitute the motive force which pushes his
intellect into action. The reading of the works of two men, neither
of them imbued with the spirit of modern science--neither of them,
indeed, friendly to that spirit--has placed me here to-day. These men
are the English Carlyle and the American Emerson. I must ever
gratefully remember that through three long cold German winters
Carlyle placed me in my tub, even when ice was on its surface, at five
o'clock every morning--not slavishly, but cheerfully, meeting each
day's studies with a resolute will, determined whether victor or
vanquished not to shrink from difficulty. I never should have gone
through Analytical Geometry and the Calculus had it not been for those
men. I never should have become a physical investigator, and hence
without them I should not have been here to-day. They told me what I
ought to do in a way that caused me to do it, and all my consequent
intellectual action is to be traced to this purely moral source. To
Carlyle and Emerson I ought to add Fichte, the greatest representative
of pure idealism. These three unscientific men made me a practical
scientific worker. They called out 'Act!' I hearkened to the
summons, taking the liberty, however, of determining for myself the
direction which effort was to take.
And I may now cry 'Act!' but the potency of action must be yours. I
may pull the trigger, but if the gun be not charged there is no
result. We are creators in the intellectual world as little as in the
physical. We may remove obstacles, and render latent capacities
active, but we cannot suddenly change the nature of man. The 'new
birth' itself implies the pre-existence of a character which requires
not to be created but brought forth. You cannot by any amount of
missionary labour suddenly transform the savage into the civilised
Christian. The improvement of man is _secular_--not the work of an hour
or of a day. But though indubitably bound by our organisations, no
man knows what the potentialities of any human mind may be, requiring
only release to be brought into action. There are in the mineral
world certain crystals--certain forms, for instance, of fluor-spar,
which have lain darkly in the earth for ages, but which nevertheless
have a potency of light locked up within them. In their case the
potential has never become actual--the light is in fact held back by a
molecular detent. When these crystals are warmed, the detent is
lifted, and an outflow of light immediately begins. I know not how
many of you may be in the condition of this fluor-spar. For aught I
know, every one of you may be in this condition, requiring but the
proper agent to be applied--the proper word to be spoken--to remove a
detent, and to render you conscious of light and warmth within
yourselves and sources of both to others.
The circle of human nature, then, is not complete without the arc of
the emotions. The lilies of the field have a value for us beyond
their botanical ones--a certain lightening of the heart accompanies
the declaration that 'Solomon in all his glory was not arrayed like
one of these.' The sound of the village bell has a value beyond its
acoustical one. The setting sun has a value beyond its optical one.
The starry heavens, as you know, had for Immanuel Kant a value beyond
their astronomical one. I think it very desirable to keep this
horizon of the emotions open, and not to permit either priest or
philosopher to draw down his shutters between you and it. Here the
dead languages, which are sure to be beaten by science in the purely
intellectual fight, have an irresistible claim. They supplement the
work of science by exalting and refining the aesthetic faculty, and
must on this account be cherished by all who desire to see human
culture complete. There must be a reason for the fascination which
these languages have so long exercised upon powerful and elevated
minds--a fascination which will probably continue for men of Greek and
Roman mould to the end of time.
In connection with this question one very obvious danger besets many
of the more earnest spirits of our day--the danger of _haste_ in
endeavouring to give the feelings repose. We are distracted by
systems of theology and philosophy which were taught to us when young,
and which now excite in us a hunger and a thirst for knowledge not
proved to be attainable. There are periods when the judgment ought to
remain in suspense, the data on which a decision might be based being
absent. This discipline of suspending the judgment is a common one in
science, but not so common as it ought to be elsewhere. I walked down
Regent Street some time ago with a man of great gifts and
acquirements, discussing with him various theological questions. I
could not accept his views of the origin and destiny of the universe,
nor was I prepared to enunciate any definite views of my own. He
turned to me at length and said, 'You surely must have a theory of the
universe.' That I should in one way or another have solved this
mystery of mysteries seemed, to my friend a matter of course. 'I have
not even a theory of magnetism' was my reply. We ought to learn to
wait. We ought assuredly to pause before closing with the advances of
those expounders of the ways of God to men, who offer us intellectual
peace at the modest cost of intellectual life.
The teachers of the world ought to be its best men, and for the
present at all events such men must learn self-trust. By the fullness
and freshness of their own Jives and utterances they must awaken life
in others. The hopes and terrors which influenced our fathers are
passing away, and our trust henceforth must rest on the innate
strength of man's moral nature. And here, I think, the poet will have
a great part to play in the future culture of the world. To him, when
he rightly understands his mission, and does not flinch from the tonic
discipline which it assuredly demands, we have a right to look for
that heightening and brightening of life which so many of us need. To
him it is given for a long time to come to fill those shores which the
recession of the theologic tide has left exposed. Void of offence to
science, he may freely deal with conceptions which science shuns, and
become the illustrator and interpreter of that Power which as
'Jehovah, Jove, or Lord,'
has hitherto filled and strengthened the human heart.
Let me utter one practical word in conclusion--take care of your
health. There have been men who by wise attention to this point might
have risen to any eminence--might have made great discoveries, written
great poems, commanded armies, or ruled states, but who by unwise
neglect of this point have come to nothing. Imagine Hercules as
oarsman in a rotten boat; what can he do there but by the very force
of his stroke expedite the ruin of his craft? Take care then of the
timbers of your boat, and avoid all practices likely to introduce
either wet or dry rot amongst them. And this is not to be
accomplished by desultory or intermittent efforts of the will, but by
the formation of _habits_. The will no doubt has sometimes to put forth
its strength in order to crush the special temptation. But the
formation of right habits is essential to your permanent security.
They diminish your chance of falling when assailed, and they augment
your chance of recovery when overthrown.
********************
If thou would'st know the mystic song
Chaunted when the sphere was young,
Aloft, abroad, the paean swells,
O wise man, hear'st thou half it tells?
To the open ear it sings
The early genesis of things;
Of tendency through endless ages
Of star-dust and star-pilgrimages,
Of rounded worlds, of space and time,
Of the old floods' subsiding slime,
Of chemic matter, force and form,
Of poles and powers, cold, wet, and warm.
The rushing metamorphosis
Dissolving all that fixture is,
Melts things that be to things that seem,
And solid nature to a dream.'
EMERSON.
Was waer' ein Gott der nur von aussen stiesse,
Im Kreis das All am Finger laufen liesse
Ihm ziemt's, die Welt im Innern zu bewegen,
Natur in Sich, Sich in Natur zu hegen.'
GOETHE.
*****
VIII. SCIENTIFIC USE OF THE IMAGINATION.
[Footnote: Discourse delivered before the British Association at
Liverpool, September 16, 1870.]
'Lastly, physical investigation, more than anything besides, helps to
teach us the actual value and right use of the Imagination--of that
wondrous faculty, which, left to ramble uncontrolled, leads us astray
into a wilderness of perplexities and errors, a land of mists and
shadows; but which, properly controlled by experience and reflection,
becomes the noblest attribute of man; the source of poetic genius, the
instrument of discovery in Science, without the aid of which Newton
would never have invented fluxions, nor Davy have decomposed the
earths and alkalies, nor would Columbus have found another
Continent.'--Address to the Royal Society by its President Sir
Benjamin Brodie, November 30, 1859.
I carried with me to the Alps this year the burden of this evening's
work. Save from memory I had no direct aid upon the mountains; but to
spur up the emotions, on which so much depends, as well as to nourish
indirectly the intellect and will, I took with me four works,
comprising two volumes of poetry, Goethe's 'Farbenlehre,' and the work
on 'Logic' recently published by Mr. Alexander Bain. In Goethe, so
noble otherwise, I chiefly noticed the self-inflicted hurts of genius,
as it broke itself in vain against the philosophy of Newton. Mr. Bain
I found, for the most part, learned and practical, shining generally
with a dry light, but exhibiting at times a flush of emotional
strength, which proved that even logicians share the common fire of
humanity. He interested me most when he became the mirror of my own
condition. Neither intellectually nor socially is it good for man to
be alone, and the sorrows of thought are more patiently borne when we
find that they have been experienced by another. From certain
passages in his book I could infer that Mr. Bain was no stranger to
such sorrows. Speaking for example of the ebb of intellectual force,
which we all from time to time experience, Mr. Bain says: 'The
uncertainty where to look for the next opening of discovery brings the
pain of conflict and the debility of indecision.' These words have in
them the true ring of personal experience. The action of the
investigator is periodic. He grapples with a subject of enquiry,
wrestles with it, and exhausts, it may be, both himself and it for the
time being. He breathes a space, and then renews the struggle in
another field. Now this period of halting between two investigations
is not always one of pure repose. It is often a period of doubt and
discomfort--of gloom and ennui. 'The uncertainty where to look for
the next opening of discovery brings the pain of conflict and the
debility of indecision.' It was under such conditions that I had to
equip myself for the hour and the ordeal that are now come.
*****
The disciplines of common life are, in great part, exercises in the
relations of space, or in the mental grouping of bodies in space; and,
by such exercises, the public mind is, to some extent, prepared for
the reception of physical conceptions. Assuming this preparation on
your part, the wish gradually grew within me to trace, and to enable
you to trace, some of the more occult features and operations of Light
and Colour. I wished, if possible, to take you beyond the boundary of
mere observation, into a region where things are intellectually
discerned, and to show you there the hidden mechanism of optical
action.
But how are those hidden things to be revealed? Philosophers may be
right in affirming that we cannot transcend experience: we can, at all
events, carry it a long way from its origin. We can magnify,
diminish, qualify, and combine experiences, so as to render them fit
for purposes entirely new. In explaining sensible phenomena, we
habitually form mental images of the ultra-sensible. There are Tories
even in science who regard Imagination as a faculty to be feared and
avoided rather than employed. They have observed its action in weak
vessels, and are unduly impressed by its disasters. But they might
with equal justice point to exploded boilers as an argument against
the use of steam. With accurate experiment and observation to work
upon, Imagination becomes the architect of physical theory. Newton's
passage from a falling apple to a falling moon was an act of the
prepared imagination, without which the 'laws of Kepler' could never
have been traced to their foundations. Out of the facts of chemistry
the constructive imagination of Dalton formed the atomic theory. Davy
was richly endowed with the imaginative faculty, while with Faraday
its exercise was incessant, preceding, accompanying and guiding all
his experiments. His strength and fertility as a discoverer is to be
referred in great part to the stimulus of his imagination. Scientific
men fight shy of the word because of its ultra-scientific
connotations; but the fact is that without the exercise of this power,
our knowledge of nature would be a mere tabulation of co-existences
and sequences. We should still believe in the succession of day and
night, of summer and winter; but the conception of Force would vanish
from our universe; causal relations would disappear, and with them
that science which is now binding the parts of nature to an organic
whole.
I should like to illustrate by a few simple instances the use that
scientific men have already made of this power of imagination, and to
indicate afterwards some of the further uses that they are likely to
make of it. Let us begin with the rudimentary experiences. Observe
the falling of heavy rain-drops into a tranquil pond. Each drop as it
strikes the water becomes a centre of disturbance, from which a series
of ring-ripples expand outwards. Gravity and inertia are the agents
by which this wave-motion is produced, and a rough experiment will
suffice to show that the rate of propagation does not amount to a foot
a second. A series of slight mechanical shocks is experienced by a
body plunged in the water, as the wavelets reach it in succession. But
a finer motion is at the same time set up and propagated. If the head
and ears be immersed in the water, as in an experiment of Franklin's,
the tick of the drop is heard. Now, this sonorous impulse is
propagated, not at the rate of a foot, but at the rate of 4,700 feet a
second. In this case it is not the gravity but the elasticity of the
water that comes into play. Every liquid particle pushed against its
neighbour delivers up its motion with extreme rapidity, and the pulse
is propagated as a thrill. The incompressibility of water, as
illustrated by the famous Florentine experiment, is a measure of its
elasticity; and to the possession of this property, in so high a
degree, the rapid transmission of a sound-pulse through water is to be
ascribed.
But water, as you know, is not necessary to the conduction of sound;
air is its most common vehicle. And you know that when the air
possesses the particular density and elasticity corresponding to the
temperature of freezing water, the velocity of sound in it is 1,090
feet a second. It is almost exactly one-fourth of the velocity in
water; the reason being that though the greater weight of the water
tends to diminish the velocity, the enormous molecular elasticity of
the liquid far more than atones for the disadvantage due to weight. By
various contrivances we can compel the vibrations of the air to
declare themselves we know the length and frequency of the sonorous
waves, and we have also obtained great mastery over the various
methods by which the air is thrown into vibration. We know the
phenomena and laws of vibrating rods, of organ-pipes, strings,
membranes, plates, and bells. We can abolish one sound by another. We
know the physical meaning of music and noise, of harmony and discord.
In short, as regards sound in general, we have a very clear notion of
the external physical processes which correspond to our sensations.
In the phenomena of sound, we travel a very little way from downright
sensible experience. Still the imagination is to some extent
exercised. The bodily eye, for example, cannot see the condensations
and rarefactions of the waves of sound. We construct them in thought,
and we believe as firmly in their existence as in that of the air
itself. But now our experience is to be carried into a new region,
where a new use is to be made of it. Having mastered the cause and
mechanism of sound, we desire to know the cause and mechanism of
light. We wish to extend our enquiries from the auditory to the optic
nerve. There is in the human intellect a power of expansion--I might
almost call it a power of creation--which is brought into play by the
simple brooding upon facts. The legend of the spirit brooding over
chaos may have originated in experience of this power. In the case
now before us it has manifested itself by transplanting into space,
for the purposes of light, an adequately modified form of the
mechanism of sound. We know intimately whereon the velocity of sound
depends. When we lessen the density of the aerial medium, and
preserve its elasticity constant, we augment the velocity. When we
heighten the elasticity, and keep the density constant, we also
augment the velocity. A small density, therefore, and a great
elasticity, are the two things necessary to rapid propagation. Now
light is known to move with the astounding velocity of 186,000 miles a
second. How is such a velocity to be obtained? By boldly diffusing
in space a medium of the requisite tenuity and elasticity.
Let us make such a medium our starting-point, and, endowing it with
one or two other necessary qualities, let us handle it in accordance
with strict mechanical laws. Let us then carry our results from the
world of theory into the world of sense, and see whether our
deductions do not issue in the very phenomena of light which ordinary
knowledge and skilled experiment reveal. If in all the multiplied
varieties of these phenomena, including those of the most remote and
entangled description, this fundamental conception always brings us
face to face with the truth; if no contradiction to our deductions
from it be found in external nature, but on all sides agreement and
verification; if, moreover, as in the case of Conical Refraction and
in other cases, it actually forces upon our attention phenomena which
no eye had previously seen, and which no mind had previously
imagined--such a conception, must, we think, be something more than a
mere figment of the scientific fancy. In forming it, that composite
and creative power, in which reason and imagination are united, has,
we believe, led us into a world not less real than that of the senses,
and of which the world of sense itself is the suggestion and, to a
great extent, the outcome.
Far be it from me, however, to wish to fix you immovably in this or in
any other theoretic conception. With all our belief of it, it will be
well to keep the theory of a luminiferous aether plastic and capable
of change. You may, moreover, urge that, although the phenomena occur
_as if_ the medium existed, the absolute demonstration of its existence
is still wanting. Far be it from me to deny to this reasoning such
validity as it may fairly claim. Let us endeavour by means of analogy
to form a fair estimate of its force. You believe that in society you
are surrounded by reasonable beings like yourself. You are, perhaps,
as firmly convinced of this as of anything. What is your warrant for
this conviction? Simply and solely this: your fellow-creatures behave
as if they were reasonable; the hypothesis, for it is nothing more,
accounts for the facts. To take an eminent example: you believe that
our President is a reasonable being. Why? There is no known method
of superposition by which any one of us can apply himself
intellectually to any other, so as to demonstrate coincidence as
regards the possession of reason. If, therefore, you hold our
President to be reasonable, it is because he behaves _as if_ he were
reasonable. As in the case of the aether, beyond the _'as if'_ you
cannot go. Nay, I should not wonder if a close comparison of the data
on which both inferences rest, caused many respectable persons to
conclude that the aether had the best of it.
This universal medium, this light-aether as it is called, is the
vehicle, not the origin, of wave-motion. It receives and transmits,
but it does not create. Whence does it derive the motions it conveys?
For the most part from luminous bodies. By the motion of a luminous
body I do not mean its sensible motion, such as the flicker of a
candle, or the shooting out of red prominences from the limb of the
sun. I mean an intestine motion of the atoms or molecules of the
luminous body. But here a certain reserve is necessary. Many
chemists of the present day refuse to speak of atoms and molecules as
real things. Their caution leads them to stop short of the clear,
sharp, mechanically intelligible atomic theory enunciated by Dalton,
or any form of that theory, and to make the doctrine of 'multiple
proportions' their intellectual bourne. I respect the caution, though
I think it is here misplaced. The chemists who recoil from these
notions of atoms and molecules accept, without hesitation, the
Undulatory Theory of Light. Like you and me they one and all believe
in an aether and its light-producing waves. Let us consider what this
belief involves. Bring your imaginations once more into play, and
figure a series of sound-waves passing through air. Follow them up to
their origin, and what do you there find? A definite, tangible,
vibrating body. It may be the vocal chords of a human being, it may
be an organ-pipe, or it may be a stretched string. Follow in the same
manner a train of aether-waves to their source; remembering at the
same time that your aether is matter, dense, elastic, and capable of
motions subject to, and determined by, mechanical laws. What then do
you expect to find as the source of a series of aether-waves? Ask
your imagination if it will accept a vibrating multiple proportion--a
numerical ratio in a state of oscillation? I do not think it will.
You cannot crown the edifice with this abstraction. The scientific
imagination, which is here authoritative, demands, as the origin and
cause of a series of aether-waves, a particle of vibrating matter
quite as definite, though it may be excessively minute, as that which
gives origin to a musical sound. Such a particle we name an atom or a
molecule. I think the intellect, when focussed so as to give
definition without penumbral haze, is sure to realise this image at
the last.
*****