A Critical Examination of "On The Origin of Species"
Thomas H. Huxley

This etext was prepared by Amy E. Zelmer.


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

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

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

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

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* 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'.

*[footnote] 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.

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

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

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

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

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.


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