













A CRITICAL EXAMINATION OF THE POSITION OF MR. DARWIN'S WORK, "ON THE
ORIGIN OF SPECIES," IN RELATION TO THE COMPLETE THEORY OF THE CAUSES OF
THE PHENOMENA OF ORGANIC NATURE


By Thomas H. Huxley




IN the preceding five lectures I have endeavoured to give you an account
of those facts, and of those reasonings from facts, which form the data
upon which all theories regarding the causes of the phenomena of organic
nature must be based. And, although I have had frequent occasion to
quote Mr. Darwin--as all persons hereafter, in speaking upon these
subjects, will have occasion to quote his famous book on the "Origin of
Species,"--you must yet remember that, wherever I have quoted him,
it has not been upon theoretical points, or for statements in any way
connected with his particular speculations, but on matters of fact,
brought forward by himself, or collected by himself, and which appear
incidentally in his book. If a man 'will' make a book, professing to
discuss a single question, an encyclopaedia, I cannot help it.

Now, having had an opportunity of considering in this sort of way the
different statements bearing upon all theories whatsoever, I have to lay
before you, as fairly as I can, what is Mr. Darwin's view of the matter
and what position his theories hold, when judged by the principles which
I have previously laid down, as deciding our judgments upon all theories
and hypotheses.

I have already stated to you that the inquiry respecting the causes of
the phenomena of organic nature resolves itself into two problems--the
first being the question of the origination of living or organic beings;
and the second being the totally distinct problem of the modification
and perpetuation of organic beings when they have already come into
existence. The first question Mr. Darwin does not touch; he does
not deal with it at all; but he says--given the origin of organic
matter--supposing its creation to have already taken place, my object is
to show in consequence of what laws and what demonstrable properties of
organic matter, and of its environments, such states of organic nature
as those with which we are acquainted must have come about. This, you
will observe, is a perfectly legitimate proposition; every person has a
right to define the limits of the inquiry which he sets before himself;
and yet it is a most singular thing that in all the multifarious, and,
not unfrequently, ignorant attacks which have been made upon the 'Origin
of Species', there is nothing which has been more speciously criticised
than this particular limitation. If people have nothing else to urge
against the book, they say--"Well, after all, you see, Mr. Darwin's
explanation of the 'Origin of Species' is not good for much, because, in
the long run, he admits that he does not know how organic matter began
to exist. But if you admit any special creation for the first particle
of organic matter you may just as well admit it for all the rest; five
hundred or five thousand distinct creations are just as intelligible,
and just as little difficult to understand, as one." The answer to these
cavils is two-fold. In the first place, all human inquiry must stop
somewhere; all our knowledge and all our investigation cannot take us
beyond the limits set by the finite and restricted character of our
faculties, or destroy the endless unknown, which accompanies, like its
shadow, the endless procession of phenomena. So far as I can venture
to offer an opinion on such a matter, the purpose of our being
in existence, the highest object that human beings can set before
themselves, is not the pursuit of any such chimera as the annihilation
of the unknown; but it is simply the unwearied endeavour to remove its
boundaries a little further from our little sphere of action.

I wonder if any historian would for a moment admit the objection, that
it is preposterous to trouble ourselves about the history of the Roman
Empire, because we do not know anything positive about the origin and
first building of the city of Rome! Would it be a fair objection to
urge, respecting the sublime discoveries of a Newton, or a Kepler,
those great philosophers, whose discoveries have been of the profoundest
benefit and service to all men,--to say to them--"After all that you
have told us as to how the planets revolve, and how they are maintained
in their orbits, you cannot tell us what is the cause of the origin of
the sun, moon, and stars. So what is the use of what you have done?"
Yet these objections would not be one whit more preposterous than the
objections which have been made to the 'Origin of Species.' Mr. Darwin,
then, had a perfect right to limit his inquiry as he pleased, and the
only question for us--the inquiry being so limited--is to ascertain
whether the method of his inquiry is sound or unsound; whether he has
obeyed the canons which must guide and govern all investigation, or
whether he has broken them; and it was because our inquiry this evening
is essentially limited to that question, that I spent a good deal of
time in a former lecture (which, perhaps, some of you thought might
have been better employed), in endeavouring to illustrate the method
and nature of scientific inquiry in general. We shall now have to put in
practice the principles that I then laid down.

I stated to you in substance, if not in words, that wherever there
are complex masses of phenomena to be inquired into, whether they be
phenomena of the affairs of daily life, or whether they belong to the
more abstruse and difficult problems laid before the philosopher, our
course of proceeding in unravelling that complex chain of phenomena with
a view to get at its cause, is always the same; in all cases we must
invent an hypothesis; we must place before ourselves some more or less
likely supposition respecting that cause; and then, having assumed an
hypothesis, having supposed cause for the phenomena in question, we must
endeavour, on the one hand, to demonstrate our hypothesis, or, on the
other, to upset and reject it altogether, by testing it in three ways.
We must, in the first place, be prepared to prove that the supposed
causes of the phenomena exist in nature; that they are what the
logicians call 'vera causae'--true causes;--in the next place, we
should be prepared to show that the assumed causes of the phenomena are
competent to produce such phenomena as those which we wish to explain by
them; and in the last place, we ought to be able to show that no other
known causes are competent to produce those phenomena. If we can succeed
in satisfying these three conditions we shall have demonstrated our
hypothesis; or rather I ought to say we shall have proved it as far as
certainty is possible for us; for, after all, there is no one of our
surest convictions which may not be upset, or at any rate modified by
a further accession of knowledge. It was because it satisfied these
conditions that we accepted the hypothesis as to the disappearance of
the tea-pot and spoons in the case I supposed in a previous lecture; we
found that our hypothesis on that subject was tenable and valid, because
the supposed cause existed in nature, because it was competent to
account for the phenomena, and because no other known cause was
competent to account for them; and it is upon similar grounds that any
hypothesis you choose to name is accepted in science as tenable and
valid.

What is Mr. Darwin's hypothesis? As I apprehend it--for I have put
it into a shape more convenient for common purposes than I could find
'verbatim' in his book--as I apprehend it, I say, it is, that all the
phenomena of organic nature, past and present, result from, or are
caused by, the inter-action of those properties of organic matter,
which we have called ATAVISM and VARIABILITY, with the CONDITIONS OF
EXISTENCE; or, in other words,--given the existence of organic matter,
its tendency to transmit its properties, and its tendency occasionally
to vary; and, lastly, given the conditions of existence by which organic
matter is surrounded--that these put together are the causes of the
Present and of the Past conditions of ORGANIC NATURE.

Such is the hypothesis as I understand it. Now let us see how it will
stand the various tests which I laid down just now. In the first place,
do these supposed causes of the phenomena exist in nature? Is it the
fact that in nature these properties of organic matter--atavism and
variability--and those phenomena which we have called the conditions of
existence,--is it true that they exist? Well, of course, if they do not
exist, all that I have told you in the last three or four lectures
must be incorrect, because I have been attempting to prove that they do
exist, and I take it that there is abundant evidence that they do exist;
so far, therefore, the hypothesis does not break down.

But in the next place comes a much more difficult inquiry:--Are the
causes indicated competent to give rise to the phenomena of organic
nature? I suspect that this is indubitable to a certain extent. It is
demonstrable, I think, as I have endeavoured to show you, that they
are perfectly competent to give rise to all the phenomena which are
exhibited by RACES in nature. Furthermore, I believe that they are
quite competent to account for all that we may call purely structural
phenomena which are exhibited by SPECIES in nature. On that point also
I have already enlarged somewhat. Again, I think that the causes assumed
are competent to account for most of the physiological characteristics
of species, and I not only think that they are competent to account
for them, but I think that they account for many things which
otherwise remain wholly unaccountable and inexplicable, and I may say
incomprehensible. For a full exposition of the grounds on which this
conviction is based, I must refer you to Mr. Darwin's work; all that I
can do now is to illustrate what I have said by two or three cases taken
almost at random.

I drew your attention, on a previous evening, to the facts which are
embodied in our systems of Classification, which are the results of
the examination and comparison of the different members of the animal
kingdom one with another. I mentioned that the whole of the animal
kingdom is divisible into five sub-kingdoms; that each of these
sub-kingdoms is again divisible into provinces; that each province may
be divided into classes, and the classes into the successively smaller
groups, orders, families, genera, and species.

Now, in each of these groups, the resemblance in structure among the
members of the group is closer in proportion as the group is smaller.
Thus, a man and a worm are members of the animal kingdom in virtue of
certain apparently slight though really fundamental resemblances which
they present. But a man and a fish are members of the same sub-kingdom
'Vertebrata', because they are much more like one another than either of
them is to a worm, or a snail, or any member of the other sub-kingdoms.
For similar reasons men and horses are arranged as members of the
same Class, 'Mammalia'; men and apes as members of the same Order,
'Primates'; and if there were any animals more like men than they
were like any of the apes, and yet different from men in important
and constant particulars of their organization, we should rank them as
members of the same Family, or of the same Genus, but as of distinct
Species.

That it is possible to arrange all the varied forms of animals into
groups, having this sort of singular subordination one to the other, is
a very remarkable circumstance; but, as Mr. Darwin remarks, this is a
result which is quite to be expected, if the principles which he lays
down be correct. Take the case of the races which are known to be
produced by the operation of atavism and variability, and the conditions
of existence which check and modify these tendencies. Take the case
of the pigeons that I brought before you; there it was shown that
they might be all classed as belonging to some one of five principal
divisions, and that within these divisions other subordinate groups
might be formed. The members of these groups are related to one
another in just the same way as the genera of a family, and the groups
themselves as the families of an order, or the orders of a class;
while all have the same sort of structural relations with the wild
rock-pigeon, as the members of any great natural group have with a real
or imaginary typical form. Now, we know that all varieties of pigeons of
every kind have arisen by a process of selective breeding from a common
stock, the rock-pigeon; hence, you see, that if all species of animals
have proceeded from some common stock, the general character of their
structural relations, and of our systems of classification, which
express those relations, would be just what we find them to be. In other
words, the hypothetical cause is, so far, competent to produce effects
similar to those of the real cause.

Take, again, another set of very remarkable facts,--the existence of
what are called rudimentary organs, organs for which we can find no
obvious use, in the particular animal economy in which they are found,
and yet which are there.

Such are the splint-like bones in the leg of the horse, which I here
show you, and which correspond with bones which belong to certain toes
and fingers in the human hand and foot. In the horse you see they are
quite rudimentary, and bear neither toes nor fingers; so that the horse
has only one "finger" in his fore-foot and one "toe" in his hind foot.
But it is a very curious thing that the animals closely allied to the
horse show more toes than he; as the rhinoceros, for instance: he has
these extra toes well formed, and anatomical facts show very clearly
that he is very closely related to the horse indeed. So we may say that
animals, in an anatomical sense nearly related to the horse, have those
parts which are rudimentary in him, fully developed.

Again, the sheep and the cow have no cutting-teeth, but only a hard
pad in the upper jaw. That is the common characteristic of ruminants in
general. But the calf has in its upper jaw some rudiments of teeth which
never are developed, and never play the part of teeth at all. Well, if
you go back in time, you find some of the older, now extinct, allies of
the ruminants have well-developed teeth in their upper jaws; and at
the present day the pig (which is in structure closely connected with
ruminants) has well-developed teeth in its upper jaw; so that here
is another instance of organs well-developed and very useful, in one
animal, represented by rudimentary organs, for which we can discover
no purpose whatsoever, in another closely allied animal. The whalebone
whale, again, has horny "whalebone" plates in its mouth, and no teeth;
but the young foetal whale, before it is born, has teeth in its jaws;
they, however, are never used, and they never come to anything.
But other members of the group to which the whale belongs have
well-developed teeth in both jaws.

Upon any hypothesis of special creation, facts of this kind appear to me
to be entirely unaccountable and inexplicable, but they cease to be so
if you accept Mr. Darwin's hypothesis, and see reason for believing that
the whalebone whale and the whale with teeth in its mouth both sprang
from a whale that had teeth, and that the teeth of the foetal whale are
merely remnants--recollections, if we may so say--of the extinct whale.
So in the case of the horse and the rhinoceros: suppose that both have
descended by modification from some earlier form which had the normal
number of toes, and the persistence of the rudimentary bones which no
longer support toes in the horse becomes comprehensible.

In the language that we speak in England, and in the language of the
Greeks, there are identical verbal roots, or elements entering into the
composition of words. That fact remains unintelligible so long as we
suppose English and Greek to be independently created tongues; but when
it is shown that both languages are descended from one original, the
Sanscrit, we give an explanation of that resemblance. In the same way
the existence of identical structural roots, if I may so term them,
entering into the composition of widely different animals, is striking
evidence in favour of the descent of those animals from a common
original.

To turn to another kind of illustration:--If you regard the whole
series of stratified rocks--that enormous thickness of sixty or seventy
thousand feet that I have mentioned before, constituting the only record
we have of a most prodigious lapse of time, that time being, in all
probability, but a fraction of that of which we have no record;--if you
observe in these successive strata of rocks successive groups of animals
arising and dying out, a constant succession, giving you the same kind
of impression, as you travel from one group of strata to another, as
you would have in travelling from one country to another;--when you find
this constant succession of forms, their traces obliterated except to
the man of science,--when you look at this wonderful history, and ask
what it means, it is only a paltering with words if you are offered the
reply,--'They were so created.'

But if, on the other hand, you look on all forms of organized beings as
the results of the gradual modification of a primitive type, the facts
receive a meaning, and you see that these older conditions are the
necessary predecessors of the present. Viewed in this light the facts of
palaeontology receive a meaning--upon any other hypothesis, I am unable
to see, in the slightest degree, what knowledge or signification we are
to draw out of them. Again, note as bearing upon the same point, the
singular likeness which obtains between the successive Faunae and
Florae, whose remains are preserved on the rocks: you never find any
great and enormous difference between the immediately successive Faunae
and Florae, unless you have reason to believe there has also been a
great lapse of time or a great change of conditions. The animals, for
instance, of the newest tertiary rocks, in any part of the world, are
always, and without exception, found to be closely allied with those
which now live in that part of the world. For example, in Europe,
Asia, and Africa, the large mammals are at present rhinoceroses,
hippopotamuses, elephants, lions, tigers, oxen, horses, etc.; and if
you examine the newest tertiary deposits, which contain the animals
and plants which immediately preceded those which now exist in the same
country, you do not find gigantic specimens of ant-eaters and kangaroos,
but you find rhinoceroses, elephants, lions, tigers, etc.,--of different
species to those now living,--but still their close allies. If you turn
to South America, where, at the present day, we have great sloths and
armadilloes and creatures of that kind, what do you find in the newest
tertiaries? You find the great sloth-like creature, the 'Megatherium',
and the great armadillo, the 'Glyptodon', and so on. And if you go to
Australia you find the same law holds good, namely, that that condition
of organic nature which has preceded the one which now exists, presents
differences perhaps of species, and of genera, but that the great types
of organic structure are the same as those which now flourish.

What meaning has this fact upon any other hypothesis or supposition than
one of successive modification? But if the population of the world, in
any age, is the result of the gradual modification of the forms which
peopled it in the preceding age,--if that has been the case, it is
intelligible enough; because we may expect that the creature that
results from the modification of an elephantine mammal shall be
something like an elephant, and the creature which is produced by the
modification of an armadillo-like mammal shall be like an armadillo.
Upon that supposition, I say, the facts are intelligible; upon any
other, that I am aware of, they are not.

So far, the facts of palaeontology are consistent with almost any
form of the doctrine of progressive modification; they would not be
absolutely inconsistent with the wild speculations of De Maillet, or
with the less objectionable hypothesis of Lamarck. But Mr. Darwin's
views have one peculiar merit; and that is, that they are perfectly
consistent with an array of facts which are utterly inconsistent with
and fatal to, any other hypothesis of progressive modification which
has yet been advanced. It is one remarkable peculiarity of Mr. Darwin's
hypothesis that it involves no necessary progression or incessant
modification, and that it is perfectly consistent with the persistence
for any length of time of a given primitive stock, contemporaneously
with its modifications. To return to the case of the domestic breeds
of pigeons, for example; you have the Dove-cot pigeon, which closely
resembles the Rock pigeon, from which they all started, existing at the
same time with the others. And if species are developed in the same way
in nature, a primitive stock and its modifications may, occasionally,
all find the conditions fitted for their existence; and though they come
into competition, to a certain extent, with one another, the derivative
species may not necessarily extirpate the primitive one, or 'vice
versa'.

Now palaeontology shows us many facts which are perfectly harmonious
with these observed effects of the process by which Mr. Darwin supposes
species to have originated, but which appear to me to be totally
inconsistent with any other hypothesis which has been proposed. There
are some groups of animals and plants, in the fossil world, which have
been said to belong to "persistent types," because they have persisted,
with very little change indeed, through a very great range of time,
while everything about them has changed largely. There are families of
fishes whose type of construction has persisted all the way from the
carboniferous rock right up to the cretaceous; and others which have
lasted through almost the whole range of the secondary rocks, and from
the lias to the older tertiaries. It is something stupendous this--to
consider a genus lasting without essential modifications through all
this enormous lapse of time while almost everything else was changed and
modified.

Thus I have no doubt that Mr. Darwin's hypothesis will be found
competent to explain the majority of the phenomena exhibited by species
in nature; but in an earlier lecture I spoke cautiously with respect to
its power of explaining all the physiological peculiarities of species.

There is, in fact, one set of these peculiarities which the theory of
selective modification, as it stands at present, is not wholly competent
to explain, and that is the group of phenomena which I mentioned to you
under the name of Hybridism, and which I explained to consist in the
sterility of the offspring of certain species when crossed one with
another. It matters not one whit whether this sterility is universal,
or whether it exists only in a single case. Every hypothesis is bound
to explain, or, at any rate, not be inconsistent with, the whole of the
facts which it professes to account for; and if there is a single one of
these facts which can be shown to be inconsistent with (I do not merely
mean inexplicable by, but contrary to) the hypothesis, the hypothesis
falls to the ground,--it is worth nothing. One fact with which it is
positively inconsistent is worth as much, and as powerful in negativing
the hypothesis, as five hundred. If I am right in thus defining the
obligations of an hypothesis, Mr. Darwin, in order to place his
views beyond the reach of all possible assault, ought to be able to
demonstrate the possibility of developing from a particular stock by
selective breeding, two forms, which should either be unable to cross
one with another, or whose cross-bred offspring should be infertile with
one another.

For, you see, if you have not done that you have not strictly fulfilled
all the conditions of the problem; you have not shown that you can
produce, by the cause assumed, all the phenomena which you have in
nature. Here are the phenomena of Hybridism staring you in the face, and
you cannot say, 'I can, by selective modification, produce these same
results.' Now, it is admitted on all hands that, at present, so far as
experiments have gone, it has not been found possible to produce this
complete physiological divergence by selective breeding. I stated this
very clearly before, and I now refer to the point, because, if it could
be proved, not only that this 'has' not been done, but that it 'cannot'
be done; if it could be demonstrated that it is impossible to breed
selectively, from any stock, a form which shall not breed with another,
produced from the same stock; and if we were shown that this must be
the necessary and inevitable results of all experiments, I hold that Mr.
Darwin's hypothesis would be utterly shattered.

But has this been done? or what is really the state of the case? It is
simply that, so far as we have gone yet with our breeding, we have
not produced from a common stock two breeds which are not more or less
fertile with one another.

I do not know that there is a single fact which would justify any one
in saying that any degree of sterility has been observed between breeds
absolutely known to have been produced by selective breeding from a
common stock. On the other hand, I do not know that there is a single
fact which can justify any one in asserting that such sterility cannot
be produced by proper experimentation. For my own part, I see every
reason to believe that it may, and will be so produced. For, as Mr.
Darwin has very properly urged, when we consider the phenomena of
sterility, we find they are most capricious; we do not know what it is
that the sterility depends on. There are some animals which will not
breed in captivity; whether it arises from the simple fact of their
being shut up and deprived of their liberty, or not, we do not know, but
they certainly will not breed. What an astounding thing this is, to
find one of the most important of all functions annihilated by mere
imprisonment!

So, again, there are cases known of animals which have been thought
by naturalists to be undoubted species, which have yielded perfectly
fertile hybrids; while there are other species which present what
everybody believes to be varieties [1] which are more or less infertile
with one another. There are other cases which are truly extraordinary;
there is one, for example, which has been carefully examined,--of two
kinds of sea-weed, of which the male element of the one, which we may
call A, fertilizes the female element of the other, B; while the male
element of B will not fertilize the female element of A; so that, while
the former experiment seems to show us that they are 'varieties', the
latter leads to the conviction that they are 'species'.

When we see how capricious and uncertain this sterility is, how unknown
the conditions on which it depends, I say that we have no right to
affirm that those conditions will not be better understood by and
by, and we have no ground for supposing that we may not be able to
experiment so as to obtain that crucial result which I mentioned
just now. So that though Mr. Darwin's hypothesis does not completely
extricate us from this difficulty at present, we have not the least
right to say it will not do so.

There is a wide gulf between the thing you cannot explain and the thing
that upsets you altogether. There is hardly any hypothesis in this
world which has not some fact in connection with it which has not been
explained, but that is a very different affair to a fact that entirely
opposes your hypothesis; in this case all you can say is, that your
hypothesis is in the same position as a good many others.

Now, as to the third test, that there are no other causes competent to
explain the phenomena, I explained to you that one should be able to say
of an hypothesis, that no other known causes than those supposed by it
are competent to give rise to the phenomena. Here, I think, Mr. Darwin's
view is pretty strong. I really believe that the alternative is either
Darwinism or nothing, for I do not know of any rational conception or
theory of the organic universe which has any scientific position at all
beside Mr. Darwin's. I do not know of any proposition that has been
put before us with the intention of explaining the phenomena of organic
nature, which has in its favour a thousandth part of the evidence which
may be adduced in favour of Mr. Darwin's views. Whatever may be the
objections to his views, certainly all others are absolutely out of
court.

Take the Lamarckian hypothesis, for example. Lamarck was a great
naturalist, and to a certain extent went the right way to work; he
argued from what was undoubtedly a true cause of some of the phenomena
of organic nature. He said it is a matter of experience that an
animal may be modified more or less in consequence of its desires and
consequent actions. Thus, if a man exercise himself as a blacksmith,
his arms will become strong and muscular; such organic modification is a
result of this particular action and exercise. Lamarck thought that by a
very simple supposition based on this truth he could explain the
origin of the various animal species: he said, for example, that the
short-legged birds which live on fish had been converted into the
long-legged waders by desiring to get the fish without wetting their
bodies, and so stretching their legs more and more through successive
generations. If Lamarck could have shown experimentally, that even races
of animals could be produced in this way, there might have been some
ground for his speculations. But he could show nothing of the kind, and
his hypothesis has pretty well dropped into oblivion, as it deserved
to do. I said in an earlier lecture that there are hypotheses and
hypotheses, and when people tell you that Mr. Darwin's strongly-based
hypothesis is nothing but a mere modification of Lamarck's, you will
know what to think of their capacity for forming a judgment on this
subject.

But you must recollect that when I say I think it is either Mr. Darwin's
hypothesis or nothing; that either we must take his view, or look upon
the whole of organic nature as an enigma, the meaning of which is
wholly hidden from us; you must understand that I mean that I accept it
provisionally, in exactly the same way as I accept any other hypothesis.
Men of science do not pledge themselves to creeds; they are bound by
articles of no sort; there is not a single belief that it is not a
bounden duty with them to hold with a light hand and to part with it
cheerfully, the moment it is really proved to be contrary to any fact,
great or small. And if, in course of time I see good reasons for such
a proceeding, I shall have no hesitation in coming before you, and
pointing out any change in my opinion without finding the slightest
occasion to blush for so doing. So I say that we accept this view as
we accept any other, so long as it will help us, and we feel bound
to retain it only so long as it will serve our great purpose--the
improvement of Man's estate and the widening of his knowledge. The
moment this, or any other conception, ceases to be useful for these
purposes, away with it to the four winds; we care not what becomes of
it!

But to say truth, although it has been my business to attend closely
to the controversies roused by the publication of Mr. Darwin's book,
I think that not one of the enormous mass of objections and obstacles
which have been raised is of any very great value, except that
sterility case which I brought before you just now. All the rest are
misunderstandings of some sort, arising either from prejudice, or want
of knowledge, or still more from want of patience and care in reading
the work.

For you must recollect that it is not a book to be read with as much
ease as its pleasant style may lead you to imagine. You spin through it
as if it were a novel the first time you read it, and think you know
all about it; the second time you read it you think you know rather less
about it; and the third time, you are amazed to find how little you have
really apprehended its vast scope and objects. I can positively say that
I never take it up without finding in it some new view, or light,
or suggestion that I have not noticed before. That is the best
characteristic of a thorough and profound book; and I believe this
feature of the 'Origin of Species' explains why so many persons have
ventured to pass judgment and criticisms upon it which are by no means
worth the paper they are written on.

Before concluding these lectures there is one point to which I must
advert,--though, as Mr. Darwin has said nothing about man in his book,
it concerns myself rather than him;--for I have strongly maintained on
sundry occasions that if Mr. Darwin's views are sound, they apply
as much to man as to the lower mammals, seeing that it is perfectly
demonstrable that the structural differences which separate man from the
apes are not greater than those which separate some apes from others.
There cannot be the slightest doubt in the world that the argument which
applies to the improvement of the horse from an earlier stock, or of ape
from ape, applies to the improvement of man from some simpler and lower
stock than man. There is not a single faculty--functional or structural,
moral, intellectual, or instinctive,--there is no faculty whatever that
is not capable of improvement; there is no faculty whatsoever which does
not depend upon structure, and as structure tends to vary, it is capable
of being improved.

Well, I have taken a good deal of pains at various times to prove this,
and I have endeavoured to meet the objections of those who maintain,
that the structural differences between man and the lower animals are of
so vast a character and enormous extent, that even if Mr. Darwin's views
are correct, you cannot imagine this particular modification to take
place. It is, in fact, easy matter to prove that, so far as structure is
concerned, man differs to no greater extent from the animals which
are immediately below him than these do from other members of the same
order. Upon the other hand, there is no one who estimates more highly
than I do the dignity of human nature, and the width of the gulf in
intellectual and moral matters, which lies between man and the whole of
the lower creation.

But I find this very argument brought forward vehemently by some. "You
say that man has proceeded from a modification of some lower animal, and
you take pains to prove that the structural differences which are
said to exist in his brain do not exist at all, and you teach that all
functions, intellectual, moral, and others, are the expression or the
result, in the long run, of structures, and of the molecular forces
which they exert." It is quite true that I do so.

"Well, but," I am told at once, somewhat triumphantly, "you say in the
same breath that there is a great moral and intellectual chasm between
man and the lower animals. How is this possible when you declare that
moral and intellectual characteristics depend on structure, and yet tell
us that there is no such gulf between the structure of man and that of
the lower animals?"

I think that objection is based upon a misconception of the real
relations which exist between structure and function, between
mechanism and work. Function is the expression of molecular forces and
arrangements no doubt; but, does it follow from this, that variation
in function so depends upon variation in structure that the former is
always exactly proportioned to the latter? If there is no such relation,
if the variation in function which follows on a variation in structure,
may be enormously greater than the variation of the structure, then, you
see, the objection falls to the ground.

Take a couple of watches--made by the same maker, and as completely
alike as possible; set them upon the table, and the function of
each--which is its rate of going--will be performed in the same manner,
and you shall be able to distinguish no difference between them; but let
me take a pair of pincers, and if my hand is steady enough to do it,
let me just lightly crush together the bearings of the balance-wheel, or
force to a slightly different angle the teeth of the escapement of one
of them, and of course you know the immediate result will be that
the watch, so treated, from that moment will cease to go. But what
proportion is there between the structural alteration and the functional
result? Is it not perfectly obvious that the alteration is of the
minutest kind, yet that slight as it is, it has produced an infinite
difference in the performance of the functions of these two instruments?

Well, now, apply that to the present question. What is it that
constitutes and makes man what he is? What is it but his power
of language--that language giving him the means of recording
his experience--making every generation somewhat wiser than its
predecessor,--more in accordance with the established order of the
universe?

What is it but this power of speech, of recording experience, which
enables men to be men--looking before and after and, in some dim
sense, understanding the working of this wondrous universe--and which
distinguishes man from the whole of the brute world? I say that this
functional difference is vast, unfathomable, and truly infinite in
its consequences; and I say at the same time, that it may depend upon
structural differences which shall be absolutely inappreciable to us
with our present means of investigation. What is this very speech that
we are talking about? I am speaking to you at this moment, but if you
were to alter, in the minutest degree, the proportion of the nervous
forces now active in the two nerves which supply the muscles of my
glottis, I should become suddenly dumb. The voice is produced only so
long as the vocal chords are parallel; and these are parallel only so
long as certain muscles contract with exact equality; and that again
depends on the equality of action of those two nerves I spoke of. So
that a change of the minutest kind in the structure of one of these
nerves, or in the structure of the part in which it originates, or of
the supply of blood to that part, or of one of the muscles to which it
is distributed, might render all of us dumb. But a race of dumb men,
deprived of all communication with those who could speak, would be
little indeed removed from the brutes. And the moral and intellectual
difference between them and ourselves would be practically infinite,
though the naturalist should not be able to find a single shadow of even
specific structural difference.

But let me dismiss this question now, and, in conclusion, let me say
that you may go away with it as my mature conviction, that Mr. Darwin's
work is the greatest contribution which has been made to biological
science since the publication of the 'Regne Animal' of Cuvier, and since
that of the 'History of Development' of Von Baer. I believe that if you
strip it of its theoretical part it still remains one of the greatest
encyclopaedias of biological doctrine that any one man ever brought
forth; and I believe that, if you take it as the embodiment of
an hypothesis, it is destined to be the guide of biological and
psychological speculation for the next three or four generations.


[Footnote 1: And as I conceive with very good reason; but if any
objector urges that we cannot prove that they have been produced by
artificial or natural selection, the objection must be admitted--
ultrasceptical as it is. But in science, scepticism is a duty.]






