science. In the revival of learning throughout the sixteenth and
seventeenth centuries, and some way on into the eighteenth century, the
common use of the Latin tongue made intercourse easy. In some respects, in
those earlier days science was more cosmopolitan than it afterwards
became. In spite of the difficulties and hardships of travel, the men of
science of different lands again and again met each other face to face,
heard with their ears, and saw with their eyes, what their brethren had to
say or show. The Englishman took the long journey to Italy to study
there; the Italian, the Frenchman, and the German wandered from one seat
of learning to another; and many a man held a chair in a country not his
own. There was help, too, as well as intercourse. The Royal Society of
London took upon itself the task of publishing nearly all the works of the
great Italian, Malpighi; and the brilliant Lavoisier, two years before his
own countrymen in their blind fury slew him, received from the same body
the highest token which it could give of its esteem.
In these closing years of the nineteenth century this great need of mutual
knowledge and of common action felt by men of science of different lands
is being manifested in a special way. Though nowadays what is done
anywhere is soon known everywhere, the news of a discovery being often
flashed over the globe by telegraph, there is an increasing activity in
the direction of organization to promote international meetings and
international cooperation. In almost every science, inquirers from many
lands now gather together at stated intervals, in international
congresses, to discuss matters which they have in common at heart, and go
away, each one feeling strengthened by having met his brother. The desire
that, in the struggle to lay bare the secrets of nature, the least waste
of human energy should be incurred, is leading more and more to the
concerted action of nations combining to attack problems the solution of
which is difficult and costly. The determination of standards of
measurement, magnetic surveys, the solution of great geodetic problems,
the mapping of the heavens and of the earth--all these are being carried
on by international organizations.
* * * * *
One international scientific effort demands a word of notice. The need
which every inquirer in science feels to know, and to know quickly, what
his fellow worker, wherever on the globe he may be carrying on his work or
making known his results, has done or is doing, led some four years back
to a proposal for carrying out by international cooperation a complete
current index, issued promptly, of the scientific literature of the world.
Though much labor in many lands has been spent upon the undertaking, the
project is not yet an accomplished fact. Nor can this, perhaps, be
wondered at, when the difficulties of the task are weighed. Difficulties
of language, difficulties of driving in one team all the several sciences
which, like young horses, wish each to have its head free with leave to go
its own way, difficulties mechanical and financial, of press and post,
difficulties raised by existing interests--these and yet other
difficulties are obstacles not easy to be overcome. The most striking and
the most encouraging features of the deliberations which have now been
going on for three years have been the repeated expressions, coming not
from this or that quarter only, but from almost all quarters, of an
earnest desire that the effort should succeed, of a sincere belief in the
good of international cooperation, and of a willingness to sink as far as
possible individual interests for the sake of the common cause. In the
face of such a spirit we may surely hope that the many difficulties will
ultimately pass out of sight.
* * * * *
I make no apology for having thus touched on international cooperation. I
should have been wanting had I not done so on the memorable occasion of
this meeting. A hundred years ago two great nations were grappling with
each other in a fierce struggle, which had lasted, with pauses, for many
years, and which was to last for many years to come; war was on every lip
and in almost every heart. To-day this meeting has, by a common wish,
been so arranged that those two nations should, in the persons of their
men of science, draw as near together as they can, with nothing but the
narrow streak of the Channel between them, in order that they may take
counsel together on matters in which they have one interest and a common
hope. May we not look upon this brotherly meeting as one of many signs
that science, though she works in a silent manner and in ways unseen by
many, is steadily making for peace?
Looking back, then, in this last year of the eighteen hundreds, on the
century which is drawing to a close, while we may see in the history of
scientific inquiry much which, telling the man of science of his
shortcomings and his weakness, bids him be humble, we also see much,
perhaps more, which gives him hope. Hope is, indeed, one of the watchwords
of science. In the latter-day writings of some who know not science much
may be read which shows that the writer is losing, or has lost, hope in
the future of mankind. There are not a few of these; their repeated
utterances make a sign of the times. Seeing in matters lying outside
science few marks of progress and many tokens of decline or decay,
recognizing in science its material benefits only, such men have thoughts
of despair when they look forward to the times to come. But if there be
any truth in what I have attempted to urge to-night, if the intellectual,
if the moral influences of science are no less marked than her material
benefits, if, moreover, that which she has done is but the earnest of that
which she shall do, such men may pluck up courage and gather strength by
laying hold of her garment.
We men of science at least need not share their views or their fears. Our
feet are set, not on the shifting sands of the opinions and the fancies of
the day, but on a solid foundation of verified truth, which by the labors
of each succeeding age is made broader and more firm. To us the past is a
thing to look back upon, not with regret, not as something which has been
lost never to be regained, but with content, as something whose influence
is with us still, helping us on our further way. With us, indeed, the past
points not to itself, but to the future; the golden age is in front of us,
not behind us; that which we do know is a lamp whose brightest beams are
shed into the unknown before us, showing us how much there is in front,
and lighting up the way to reach it. We are confident in the advance
because, as each one of us feels that any step forward which he may make
is not ordered by himself and is not the result of his own sole efforts in
the present, but is, and that in large measure, the outcome of the labors
of others in the past, so each one of us has the sure and certain hope
that, as the past has helped him, so his efforts, be they great or be they
small, will be a help to those to come.
THOMAS HENRY HUXLEY
THREE HYPOTHESES RESPECTING THE HISTORY OF NATURE
So far as I know, there are only three hypotheses which ever have been
entertained, or which well can be entertained, respecting the past history
of nature. I will, in the first place, state the hypotheses, and then I
will consider what evidence bearing upon them is in our possession, and by
what light of criticism that evidence is to be interpreted.
Upon the first hypothesis, the assumption is, that phenomena of nature
similar to those exhibited by the present world have always existed; in
other words, that the universe has existed from all eternity in what may
be broadly termed its present condition.
The second hypothesis is, that the present state of things has had only a
limited duration, and that, at some period in the past, a condition of the
world, essentially similar to that which we now know, came into existence,
without any precedent condition from which it could have naturally
proceeded. The assumption that successive states of nature have arisen,
each without any relation of natural causation to an antecedent state, is
a mere modification of this second hypothesis.
The third hypothesis also assumes that the present state of things has had
but a limited duration; but it supposes that this state has been evolved
by a natural process from an antecedent state, and that from another, and
so on; and, on this hypothesis, the attempt to assign any limit to the
series of past changes is, usually, given up.
It is so needful to form clear and distinct notions of what is really
meant by each of these hypotheses, that I will ask you to imagine what,
according to each, would have been visible to a spectator of the events
which constitute the history of the earth. On the first hypothesis,
however far back in time that spectator might be placed, he would see a
world essentially, though perhaps not in all its details, similar to that
which now exists. The animals which existed would be the ancestors of
those which now live, and similar to them; the plants, in like manner,
would be such as we know; and the mountains, plains, and waters would
foreshadow the salient features of our present land and water. This view
was held more or less distinctly, sometimes combined with the notion of
recurrent cycles of change, in ancient times; and its influence has been
felt down to the present day.
It is worthy of remark that it is a hypothesis which is not inconsistent
with the doctrine of Uniformitarianism, with which geologists are
familiar. That doctrine was held by Hutton, and in his earlier days by
Lyell. Hutton was struck by the demonstration of astronomers that the
perturbations of the planetary bodies, however great they may be, yet
sooner or later right themselves; and that the solar system possesses a
self-adjusting power by which these aberrations are all brought back to a
mean condition. Hutton imagined that the like might be true of terrestrial
changes; although no one recognized more clearly than he the fact that the
dry land is being constantly washed down by rain and rivers, and deposited
in the sea; and that thus, in a longer or shorter time, the inequalities
of the earth's surface must be leveled, and its high lands brought down to
the ocean. But, taking into account the internal forces of the earth,
which, upheaving the sea-bottom, give rise to new land, he thought that
these operations of degradation and elevation might compensate each other;
and that thus, for any assignable time, the general features of our
planet might remain what they are. And inasmuch as, under these
circumstances, there need be no limit to the propagation of animals and
plants, it is clear that the consistent working-out of the uniformitarian
idea might lead to the conception of the eternity of the world. Not that I
mean to say that either Hutton or Lyell held this conception--assuredly
not; they would have been the first to repudiate it. Nevertheless, the
logical development of their arguments tends directly toward this
hypothesis.
The second hypothesis supposes that the present order of things, at some
no very remote time, had a sudden origin, and that the world, such as it
now is, had chaos for its phenomenal antecedent. That is the doctrine
which you will find stated most fully and clearly in the immortal poem of
John Milton,--the English "Divina Commoedia,"--"Paradise Lost." I
believe it is largely to the influence of that remarkable work, combined
with the daily teachings to which we have all listened in our childhood,
that this hypothesis owes its general wide diffusion as one of the current
beliefs of English-speaking people. If you turn to the seventh book of
"Paradise Lost," you will find there stated the hypothesis to which I
refer, which is briefly this: that this visible universe of ours came into
existence at no great distance of time from the present; and that the
parts of which it is composed made their appearance, in a certain definite
order, in the space of six natural days, in such a manner that, on the
first of these days, light appeared; that, on the second, the firmament,
or sky, separated the waters above from the waters beneath the firmament;
that, on the third day, the waters drew away from the dry land, and upon
it a varied vegetable life, similar to that which now exists, made its
appearance; that the fourth day was signalized by the apparition of the
sun, the stars, the moon, and the planets; that, on the fifth day, aquatic
animals originated within the waters; that, on the sixth day, the earth
gave rise to our four-footed terrestrial creatures, and to all varieties
of terrestrial animals except birds, which had appeared on the preceding
day; and, finally, that man appeared upon the earth, and the emergence of
the universe from chaos was finished. Milton tells us, without the least
ambiguity, what a spectator of these marvelous occurrences would have
witnessed. I doubt not that his poem is familiar to all of you, but I
should like to recall one passage to your minds, in order that I may be
justified in what I have said regarding the perfectly concrete, definite
picture of the origin of the animal world which Milton draws. He says:--
The sixth, and of creation last, arose
With evening harps and matin, when God said,
"Let the earth bring forth soul living in her kind,
Cattle and creeping things, and beast of the earth,
Each in their kind!" The earth obeyed, and, straight
Opening her fertile womb, teemed at a birth
Innumerous living creatures, perfect forms,
Limbed and full-grown. Out of the ground uprose,
As from his lair, the wild beast, where he wons
In forest wild, in thicket, brake, or den;
Among the trees in pairs they rose, they walked;
The cattle in the fields and meadows green;
Those rare and solitary; these in flocks
Pasturing at once, and in broad herds upsprung.
The grassy clods now calved; now half appears
The tawny lion, pawing to get free
His hinder parts--then springs, as broke from bonds,
And rampant shakes his brinded mane; the ounce,
The libbard, and the tiger, as the mole
Rising, the crumbled earth above them threw
In hillocks; the swift stag from underground
Bore up his branching head; scarce from his mould
Behemoth, biggest born of earth, upheaved
His vastness; fleeced the flocks and bleating rose
As plants; ambiguous between sea and land,
The river-horse and scaly crocodile.
At once came forth whatever creeps the ground,
Insect or worm.
There is no doubt as to the meaning of this statement, nor as to what a
man of Milton's genius expected would have been actually visible to an
eye-witness of this mode of origination of living things.
The third hypothesis, or the hypothesis of evolution, supposes that, at
any comparatively late period of past time, our imaginary spectator would
meet with a state of things very similar to that which now obtains; but
that the likeness of the past to the present would gradually become less
and less, in proportion to the remoteness of his period of observation
from the present day; that the existing distribution of mountains and
plains, of rivers and seas, would show itself to be the product of a slow
process of natural change operating upon more and more widely different
antecedent conditions of the mineral framework of the earth; until, at
length, in place of that framework, he would behold only a vast nebulous
mass, representing the constituents of the sun and of the planetary
bodies. Preceding the forms of life which now exist, our observer would
see animals and plants, not identical with them, but like them; increasing
their difference with their antiquity and, at the same time, becoming
simpler and simpler; until, finally, the world of life would present
nothing but that undifferentiated protoplasmic matter which, so far as our
present knowledge goes, is the common foundation of all vital activity.
The hypothesis of evolution supposes that, in all this vast progression,
there would be no breach of continuity, no point at which we could say,
"This is a natural process," and, "This is not a natural process"; but
that the whole might be compared to that wonderful process of development
which may be seen going on every day under our eyes, in virtue of which
there arises, out of the semifluid, comparatively homogeneous substance
which we call an egg, the complicated organization of one of the higher
animals. That, in a few words, is what is meant by the hypothesis of
evolution.
I have already suggested that, in dealing with these three hypotheses, in
endeavoring to form a judgment as to which of them is the more worthy of
belief, or whether none is worthy of belief,--in which case our condition
of mind should be that suspension of judgment which is so difficult to all
but trained intellects,--we should be indifferent to all _a priori_
considerations. The question is a question of historical fact. The
universe has come into existence somehow or other, and the problem is,
whether it came into existence in one fashion, or whether it came into
existence in another; and, as an essential preliminary to further
discussion, permit me to say two or three words as to the nature and the
kinds of historical evidence.
The evidence as to the occurrence of any event in past time may be ranged
under two heads, which, for convenience' sake, I will speak of as
testimonial evidence and as circumstantial evidence. By testimonial
evidence I mean human testimony; and by circumstantial evidence I mean
evidence which is not human testimony. Let me illustrate by a familiar
example what I understand by these two kinds of evidence, and what is to
be said respecting their value.
Suppose that a man tells you that he saw a person strike another and kill
him: that is testimonial evidence of the fact of murder. But it is
possible to have circumstantial evidence of the fact of murder: that is to
say, you may find a man dying with a wound upon his head having exactly
the form and character of the wound which is made by an axe; and, with due
care in taking surrounding circumstances into account, you may conclude
with the utmost certainty that the man has been murdered; that his death
is the consequence of a blow inflicted by another man with that implement.
We are very much in the habit of considering circumstantial evidence as of
less value than testimonial evidence; and it may be that, where the
circumstances are not perfectly clear and intelligible, it is a dangerous
and unsafe kind of evidence; but it must not be forgotten that, in many
cases, circumstantial is quite as conclusive as testimonial evidence, and
that, not unfrequently, it is a great deal weightier than testimonial
evidence. For example, take the case to which I referred just now. The
circumstantial evidence may be better and more convincing than the
testimonial evidence; for it may be impossible, under the conditions that
I have defined, to suppose that the man met his death from any cause but
the violent blow of an axe wielded by another man. The circumstantial
evidence in favor of a murder having been committed, in that case, is as
complete and as convincing as evidence can be. It is evidence which is
open to no doubt and to no falsification. But the testimony of a witness
is open to multitudinous doubts. He may have been mistaken. He may have
been actuated by malice. It has constantly happened that even an accurate
man has declared that a thing has happened in this, that, or the other
way, when a careful analysis of the circumstantial evidence has shown that
it did not happen in that way, but in some other way.
We may now consider the evidence in favor of or against the three
hypotheses. Let me first direct your attention to what is to be said about
the hypotheses of the eternity of the state of things in which we now
live. What will first strike you is, that it is a hypothesis which,
whether true or false, is not capable of verification by any evidence.
For, in order to obtain either circumstantial or testimonial evidence
sufficient to prove the eternity of duration of the present state of
nature, you must have an eternity of witnesses or an infinity of
circumstances, and neither of these is attainable. It is utterly
impossible that such evidence should be carried beyond a certain point of
time; and all that could be said, at most, would be, that, so far as the
evidence could be traced, there was nothing to contradict the hypothesis.
But when you look, not to the testimonial evidence,--which, considering
the relative insignificance of the antiquity of human records, might not
be good for much in this case,--but to the circumstantial evidence, then
you find that this hypothesis is absolutely incompatible with such
evidence as we have; which is of so plain and so simple a character that
it is impossible in any way to escape from the conclusions which it forces
upon us.
You are, doubtless, all aware that the outer substance of the earth, which
alone is accessible to direct observation, is not of a homogeneous
character, but that it is made up of a number of layers or strata. Each of
these groups represents a number of beds of sand, of stone, of clay, of
slate, and of various other materials.
On careful examination, it is found that the materials of which each of
these layers of more or less hard rock is composed are, for the most part,
of the same nature as those which are at present being formed under known
conditions on the surface of the earth. For example, the chalk, which
constitutes a great part of the Cretaceous formation in some parts of the
world, is practically identical in its physical and chemical characters
with a substance which is now being formed at the bottom of the Atlantic
Ocean, and covers an enormous area; other beds of rock are comparable with
the sands which are being formed upon sea-shores, packed together, and so
on. Thus, omitting rocks of igneous origin, it is demonstrable that all
these beds of stone, of which a total of not less than seventy thousand
feet is known, have been formed by natural agencies, either out of the
waste and washing of the dry land, or else by the accumulation of the
exuviae of plants and animals. Many of these strata are full of such
exuviae--the so-called "fossils." Remains of thousands of species of
animals and plants, as perfectly recognizable as those of existing forms
of life which you meet with in museums, or as the shells which you pick up
upon the sea-beach, have been imbedded in the ancient sands, or muds, or
limestones, just as they are being imbedded now in sandy, or clayey, or
calcareous subaqueous deposits. They furnish us with a record, the general
nature of which cannot be misinterpreted, of the kinds of things that have
lived upon the surface of the earth during the time that is registered by
this great thickness of stratified rocks.
But even a superficial study of these fossils shows us that the animals
and plants which live at the present time have had only a temporary
duration; for the remains of such modern forms of life are met with, for
the most part, only in the uppermost, or latest, tertiaries, and their
number rapidly diminishes in the lower deposits of that epoch. In the
older tertiaries, the places of existing animals and plants are taken by
other forms, as numerous and diversified as those which live now in the
same localities, but more or less different from them; in the mesozoic
rocks, these are replaced by others yet more divergent from modern types;
and in the palaeozoic formations, the contrast is still more marked. Thus
the circumstantial evidence absolutely negatives the conception of the
eternity of the present condition of things. We can say with certainty
that the present condition of things has existed for a comparatively short
period; and that, so far as animal and vegetable nature are concerned, it
has been preceded by a different condition. We can pursue this evidence
until we reach the lowest of the stratified rocks, in which we lose the
indications of life altogether. The hypothesis of the eternity of the
present state of nature may, therefore, be put out of court.