SPONTANEOUS GENERATION, 
AND THE HYPOTHESIS 01’ 
PHYSIOLOGrICAL UNITS. 
A REPLY 
TO 
THE NORTH AMERICAN REVIEW. 
HERBERT SPENCER. 
NEW YORK: 
D. APPLETON & COMPANY, 
90, 92 & 94 GRAND STREET. 
1870. Works of Herbert Spence,r published by D. Appleton dc Co. 
ILLUSTRATIONS OF UNIVERSAL PROGRESS 
A SERIES OF DISCUSSIONS. 
1 Vol Large 12mo. 470 Pages. Price 
contents: 
.American Notice of Spencer’s New System of Philosophy. 
I, Progress: its Law and Cause. 
II Manners and Fashion. 
III. The Genesis of Science. 
IV. The Physiology of Laughter. 
Y. The Origin and Function of Music. 
VI. The Nebular Hypothesis. 
VII. Bain on the Emotions and the Will. 
VIII. Illogical Geology. 
IX. The Development Hypothesis. 
X. The Social Organism. 
XI. Use and Beauty. 
XII. The Sources of Architectural Types. 
XIII. The Use of Anthropomorphism. 
These Essays constitute a body of massive and original thought upon a 
targe variety of important topics, and will be read with pleasure by all who 
appreciate a bold and powerful treatment of fundamental themes. The 
general thought which pervades this book is beyond doubt the most impor 
tant that the human mind has yet reached.—N. Y. Independent. 
Those who have read the work on Education, will remember the ana- 
lytic tendency of the author’s mind—his clear perception and admirable ex- 
position of first principles—his wide grasp of facts—his lucid and vigorous 
style, and the constant and controlling bearing of the discussion on practical 
results. These traits characterize all Mr. Spencer’s writings, and mark, in 
an eminent degree, the present volume.—N. Y. Tribune. 
We regard the distinguishing feature of this work to be the peculiarly 
Interesting character of its matter to the general reader. This is a great 
literary as well as philosophic triumph. In the evolution of a system of 
Philosophy which demands serious attention, and a keen exercise of the in- 
tellect to fathom and appreciate, he has mingled much that is really populai 
»nd entertaining.—Rochester Democrat. SPONTANEOUS GENERATION, 
AND THE HYPOTHESIS OF 
PHYSIOLOGICAL UNITS. 
A REPLY 
TO 
THE NORTH AMERICAN REVIEW. 
HERBERT SPENCER. 
BY 
NEW YORK: 
D. APPLETON AND COMPANY, 
90, 93 & 94 GRAND STREET. 
1870. PUBLISHERS’ NOTE. 
The following letter was originally written for publication in the North 
American Review ; but, in pursuance of a general rule not to admit replies, the 
editor declined it. To prevent misapprehension in regard to his views, hoivever, 
Mr. Spencer designed to introduce it as an appendix to vol. 1 of the “ Principles of 
Biology.'''1 A portion of it having been published in Appletons’ Journal, has 
awakened so much interest among men of science, that it has been thought desirable 
to issue it in this separate form. ON ALLEGED “SPONTANEOUS GENERATION," AND ON 
TIIE HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
The Editor of the North American Review. 
Sir : It is in most cases unwise to notice adverse criticisms. 
Either they do not admit of answers, or the answers may be left to 
the penetration of readers. When, however, a critic’s allegations 
touch the fundamental propositions of a book, and especially 
when they appear in a periodical having the position of the 
North American Review, the case is altered. For these reasons 
the article on “ Philosophical Biology,” published in your last 
number, demands from me an attention which ordinary criticisms 
do not. 
It is the more needful for me to notice it, because its two lead- 
ing objections have the one an actual fairness and the other an 
apparent fairness; and, in the absence of explanations from me, 
they will be considered as substantiated even by many, or per- 
haps most, of those who have read the work itself—much more 
by those who have not read it. That, to prevent the spread of 
misapprehensions, I ought to say something, is further shown by 
the fact that the same two objections have already been made in 
England—the one by Dr. Child, of Oxford, in his Essays on Phys- 
iological Subjects, and the other by a writer in the Westminster 
Review for July, I860. 
In the note to which your reviewer refers, I have, as he says, 
tacitly repudiated the belief in “ spontaneous generation ; ” and 
that I have done this in such a way as to leave open the door for 
the interpretation given by him is true. Indeed, the fact that 
Dr. Child, whose criticism is a sympathetic one, puts the same 4 
SPONTANEOUS GENERATION, AND THE 
construction on this note, proves that your reviewer has but 
drawn what seems to be a necessary inference. Nevertheless, 
the inference is one which I did not intend to be drawn. 
In explanation, let me at the outset remark that I am placed 
at a disadvantage in having had to omit that part of the System 
of Philosophy which deals with Inorganic Evolution. In the 
original programme will be found a parenthetic reference to this 
omitted part, which should, as there stated, precede the Princi- 
ples of Biology. Two volumes are missing. The closing chap- 
ter of the second, were it written, would deal with the evolution 
of organic matter—the step preceding the evolution of living 
forms. Habitually carrying with me in thought the contents of 
this unwritten chapter, I have, in some cases, expressed myself 
as though the reader had it before him; and have thus rendered 
some of my statements liable to misconstructions. Apart from 
this, however, the explanation of the apparent inconsistency is 
very simple, if not very obvious. In the first place, I do not be- 
lieve in the “ spontaneous generation ” commonly alleged, and 
referred to in the note; and so little have I associated in thought 
this alleged “spontaneous generation” which I disbelieve, with 
the generation by evolution which I do believe, that the repudia- 
tion of the one never occurred to me as liable to be taken for re- 
pudiation of the other. That creatures having quite specific struc- 
tures are evolved in the course of a few hours, without antece- 
dents calculated to determine their specific forms, is to me incred- 
ible. Not only the established truths of Biology, but the estab- 
lished truths of science in general, negative the supposition that 
organisms, having structures definite enough to identify them as 
belonging to known genera and species, can be produced in the 
absence of germs derived from antecedent organisms of the same 
genera and species. If there can suddenly be imposed on simple 
protoplasm the organization which constitutes it a Paramoecium, 
I see no reason why animals of greater complexity, or indeed of 
any complexity, may not be constituted after the same manner. 
In brief, I do not accept these alleged facts as exemplifying Evolu- 
tion, because they imply something immensely beyond that which 
Evolution, as I understand it, can achieve. In the second place, 
my disbelief extends not only to the alleged cases of “ spontaneous 
generation,” but to every case akin to them. The very concep- 
tion of spontaneity is wholly incongruous with the conception of 
Evolution. For this reason I regard as objectionable Mr. Dar- 
win’s phrase “ spontaneous variation” (as indeed he does him- 
self) ; and I have sought to show that there are always assign- 
able causes of variation. No form of Evolution, inorganic or or- 
ganic, can be spontaneous; but in every instance the antecedent 
forces must be adequate in their quantities, kinds, and distribu- 
tions, to work the observed effects. Neither the alleged cases of HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
5 
“ spontaneous generation,” nor any imaginable cases in tlie least 
allied to them, fulfil this requirement. 
If, accepting these alleged eases of “ spontaneous generation,” 
I had assumed, as your reviewer seems to do, that the evolution 
of organic life commenced in an analogous way; then, indeed, I 
should have left myself open to a fatal criticism. This supposed 
“ spontaneous generation ” habitually occurs in menstrua that con- 
tain either organic matter, or matter originally derived from or- 
ganisms ; and such organic matter, proceeding in all known cases 
from organisms of a higher kind, implies the preexistence of such 
higher organisms. By what kind of logic, then, is it inferrible 
that organic life was initiated after a manner like that in which 
Infusoria are said to be now spontaneously generated ? Where, 
before life commenced, were the superior organisms from which 
these lowest organisms obtained their organic matter ? Without 
doubting that there are those who, as the reviewer says, “ can 
penetrate deeper than Mr. Spencer has done into the idea of uni- 
versal evolution,” and who, as he contends, prove this by accept- 
ing the doctrine of “spontaneous generation,” I nevertheless 
think that I can penetrate deep enough to see that a tenable hy- 
pothesis respecting the origin of organic life must be reached by 
some other clew than that furnished by experiments on decoction 
of hay and extract of beef. 
From what I do not believe, let me now pass to what I do be- 
lieve. Granting that the formation of organic matter, and the 
evolution of life in its lowest forms, may go on under existing 
cosmical conditions; but believing it more likely that the forma- 
tion of such matter and such forms took place at a time when 
the heat of the Earth’s surface was falling through those ranges 
of temperature at which the higher organic compounds are un- 
stable ; I conceive that the moulding of such organic matter into 
the simplest types must have commenced with portions of pro- 
toplasm more minute, more indefinite, and more inconstant in 
their characters, than the lowest Rhizopods—less distinguishable 
from a mere fragment of albumen than even the Protogenes of 
Professor Haeckel. The evolution of specific shapes must, like 
all other organic evolution, have resulted from the actions and re- 
actions between such incipient types and their environments, 
and the continued survival of those which happened to have spe- 
cialties best fitted to the specialties of their environments. To 
reach by this process the comparatively well-specialized forms of 
ordinary Infusoria, must, I conceive, have taken an enormous 
period of time. 
To prevent, as far as may be, future misapprehension, let me 
elaborate this conception so as to meet the particular objections 
raised. The reviewer takes for granted that a “first organism” 
must be assumed by me, as it is by himself. But the conception 6 
SPONTANEOUS GENERATION, AND TIIE 
of a “ first organism,” in any tiling like the current sense of the 
words, is wholly at variance with conception of evolution; and 
scarcely less at variance with tha facts revealed by the micro- 
scope. The lowest living tilings are not, properly speaking, or- 
ganisms at all; for they have no distinctions of parts—no traces 
of organization. It is almost a misuse of language to call them 
“ forms ” of life : not only are their outlines, when distinguishable, 
too unspecific for description, but they change from moment to 
moment and are never twice alike, either in two individuals or in 
the same individual. Even the word “ type ” is applicable in but 
a loose way; for there is little constancy in their generic charac- 
ters : according as the surrounding conditions determine, they un- 
dergo transformations now of one kind and now of another. And 
the vagueness, the inconstancy, the want of appreciable struc- 
ture, displayed by the simplest of living things as we now see 
them, are characters (or absences of characters) which, on the 
hypothesis of Evolution, must have been still more decided when, 
as at first, no “ forms,” no “ types,” no “ specific shapes,” had 
been moulded. That “ absolute commencement of organic life 
on the globe,” which the reviewer says I “ cannot evade the ad- 
mission of,” I distinctly deny. The affirmation of universal evo- 
lution is in itself the negation of an “ absolute commencement ” 
of any thing. Construed in terms of evolution, every kind of 
being is conceived as a product of modifications wrought by in- 
sensible gradations on a preexisting kind of being; and this 
holds as fully of the supposed “ commencement of organic life ” 
as of all subsequent developments of organic life. It is no more 
needful to suppose an “ absolute commencement of organic life ” 
or a “ first organism,” than it is needful to suppose an absolute 
commencement of social life and a first social organism. The as- 
sumption of such a necessity in this last case, made by early 
speculators with their theories of “ social contracts ” and the like, 
is disproved by the facts; and the facts, so far as they are ascer- 
tained, disprove the assumption of such a necessity in the first 
case. That organic matter was not produced all at once, but was 
reached through steps, we are well warranted in believing by the 
experiences of chemists. Organic matters are produced in the 
laboratory by what we may literally call artificial evolution. 
Chemists find themselves unable to form these complex combina- 
tions directly from their elements; but they succeed in forming 
them indirectly, by successive modifications of simpler combina- 
tions. In some binary compound, one element of which is pres- 
ent in several equivalents, a change is iriade by substituting for 
one of these equivalents an equivalent of some other element; so 
producing a ternary compound. Then another of the equivalents 
is replaced, and so on. For instance, beginning with ammonia, 
NH3, a higher form is obtained by replacing one of the atoms of HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
7 
hydrogen by an atom of methyl, so producing methyl-amine, N 
(C H3 H„); and then, under the further action of methyl, ending 
in a further substitution, there is reached the still more com- 
pound substance dimethyl-amine, N (0 H3) (0 H3) H. And in 
this manner highly-complex substances are eventually built up. 
Another characteristic of their method is no less .significant. 
Two complex compounds are employed to generate, by their ac- 
tion upon one another, a compound of still greater complexity: 
different heterogeneous molecules of one stage become parents 
of a molecule a stage higher in heterogeneity. Thus, having- 
built up acetic acid out of its elements, and having, by the pro- 
cess of substitution described above, changed the acetic acid 
into propionic acid, and propionic into butyric, of which the for- 
mula is | q $$>Qf j-; this complex compound, by oper- 
ating on another complex compound, such as the dimethyl-amine 
named above, generates one of still greater complexity, butyrate 
of dimethyl-amine j H»). H j- N (C Ha) (C H3) H. 
See, then, the remarkable parallelism. The progress toward 
higher types of organic molecules is effected by modifications 
upon modifications; as throughout Evolution in general. Each 
of these modifications is a change of the molecule into equilibri- 
um with its environment—an adaptation, as it were, to new sur- 
rounding conditions to which it is subjected; as throughout 
Evolution in general. Larger, or more integrated, aggregates 
(for compound molecules are such) are successively generated; 
as throughout Evolution in general. More complex or hetero- 
geneous aggregates are so made to arise, one out of another; as 
throughout Evolution in general. A geometrically-increasing 
multitude of these larger and more complex aggregates so pro- 
duced, at the same time results ; as throughout Evolution in gen- 
eral. And it is by the action of the successively higher forms on 
one another, joined with the action of environing conditions, that 
the highest forms are reached; as throughout Evolution in gen- 
eral. 
When we thus see the identity of method at the two ex- 
tremes—when we see that the general laws of evolution, as they 
are exemplified in known organisms, have been unconsciously 
conformed to by chemists in the artificial evolution of organic 
matter; we can scarcely doubt that these laws were conformed 
to in the natural evolution of organic matter, and afterward in 
the evolution of the simplest organic forms. In the early world, 
as in the modern laboratory, inferior types of organic substances, 
by their mutual actions under fit conditions, evolved the superior 
types of organic substances, ending in organizable protoplasm. 
And it can hardly be doubted that the shaping of organizable 8 
SPONTANEOUS GENERATION, AND THE 
protoplasm, which is a substance modifiable in multitudinous 
ways with extreme facility, went on after the same manner. As 
I learn from one of our first chemists, Prof. Frankland, protein is 
capable of existing under probably at least a thousand isomeric 
forms; and, as we shall presently see, it is capable of forming, 
with itself and other elements, substances yet more intricate in 
composition, that are practically infinite in their varieties of kind. 
Exposed to those innumerable modifications of conditions which 
the Earth’s surface afforded, here in amount of light, there in 
amount of heat, and elsewhere in the mineral quality of its 
aqueous medium, this extremely changeable substance must have 
undergone now one, now another, of its countless metamorpho- 
ses. And to the mutual influences of its metamorphic forms 
under favoring conditions, we may ascribe the production of the 
still more composite, still more sensitive, still more variously- 
changeable portions of organic matter, which, in masses more 
minute and simpler than existing Protozoa, displayed actions 
verging little by little into those called vital—actions which pro- 
tein itself exhibits in a certain degree, and which the lowest 
known living things exhibit only in a greater degree. Thus, 
setting out with inductions from the experiences of organic chem- 
ists at the one extreme, and with inductions from the observa- 
tions of biologists at the other extreme, we are enabled deduc- 
tively to bridge the interval—are enabled to conceive how or- 
ganic compounds were evolved, and how, by a continuance of 
the process, the nascent life displayed in these became gradually 
more pronounced. And this it is which has to be explained, and 
which the alleged cases of “ spontaneous generation ” would not, 
were they substantiated, help us in the least to explain. 
It is thus manifest, I think, that I have not fallen into the al- 
leged inconsistency. Nevertheless, I admit that your reviewer 
was justified in inferring this inconsistency ; and I take blame to 
myself for not having seen that the statement, as I have left it, is 
open to misconstruction. 
I pass now to the second allegation—that in ascribing to cer- 
tain specific molecules, which I have called “ physiological units,” 
the aptitude to build themselves into the structure of the organ- 
ism to which they are peculiar, I have abandoned my own prin- 
ciple, and have assumed something beyond the redistribution of 
Matter and Motion. As put by the reviewer, his case appears to 
be well made out; and that he is not altogether unwarranted in 
so putting it, may be admitted. Nevertheless, there does not in 
reality exist the supposed incongruity. 
Before attempting to make clear the adequacy of the concep- 
tion which I am said to have tacitly abandoned as insufficient, let 
me remove that excess of improbability the reviewer gives to it, HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
by the extremely-restricted meaning with which he uses the 
word mechanical. In discussing a proposition of mine he says : 
“ He then cites certain remarks of Mr. Paget on the permanent effects 
wrought in the blood by the poison of scarlatina and small-pox, as justifying 
the belief that such a ‘ power ’ exists, and attributes the repair of a wasted tis- 
sue to ‘ forces analogous to those by which a crystal reproduces its lost apex.’ 
(Neither of which phenomena, however, is explicable by mechanical causes.)” 
Were it not for the deliberation with which this last state- 
ment is made, I should take it for a slip of the pen. As it is, 
however, I have no course left but to suppose the reviewer un- 
aware of the fact that molecular actions of all kinds are now not 
only conceived as mechanical actions, but that calculations based 
on this conception of them bring out the results that correspond 
with observation. There is no kind of rearrangement among 
molecules (crystallization being one) which the modern physicist 
does not think of, and correctly reason upon, in terms of forces 
and motions like those of sensible masses. Polarity is regarded 
as a resultant of such forces and motions; and when, as happens 
in many cases, light changes the molecular structure of a crystal, 
and alters its polarity, it does this by impressing, in conformity 
with mechanical laws, new motions on the constituent molecules. 
That the reviewer should present the mechanical conception 
under so extremely limited a form, is the more surprising to me 
because, at the outset of the very work he reviews, I have, in va- 
rious passages, based inferences on those immense extensions of 
it which he ignores; indicating, for example, the interpretation 
it yields of the inorganic chemical changes effected by heat, and 
the organic chemical changes effected by light (Principles of 
Biology, § 13). 
Premising, then, that the ordinary idea of mechanical action 
must be greatly expanded, let us enter upon the question at is- 
sue—the sufficiency of the hypothesis that the structure of each 
organism is determined by the polarities of the special molecules, 
or physiological units, peculiar to it as a species, which necessi- 
tate tendencies toward special arrangements. My proposition 
and the reviewer’s criticism upon it will be most conveniently 
presented if I quote in full a passage of his from which I have 
already extracted some expressions. He says: 
“ It will be noticed, however, that Mr. Spencer attributes the possession 
of these 1 tendencies,’ or ‘ proclivities,’ to natural inheritance from ancestral or- 
ganisms ; and it may be argued that he thus saves the mechanist theory and 
his own consistency at the same time, inasmuch as he derives even the ‘ tenden- 
cies’themselves ultimately from the environment. To this we reply, that Mr. 
Spencer, who advocates the nebular hypothesis, cannot evade the admission of 
an absolute commencement of organic life on the globe, and that the ‘ forma- 
tive tendencies,’ without which he cannot explain the evolution of a single indi- 
vidual, could not have been inherited by the first organism. Besides, by his 
virtual denial of spontaneous generation, he denies that the first organism was 10 
SPONTANEOUS GENERATION, AND THE 
evolved out of the inorganic world, and thus shuts himself off from the argu- 
ment ( otherwise plausible) that its ‘ tendencies ’ were ultimately derived from 
the environment.” 
This assertion is already in great measure disposed of by what 
has been said above. Holding that, though not “ spontaneously 
generated,” those minute portions of protoplasm which first dis- 
played in the feeblest degree that changeability taken to imply 
life, were evolved, I am not debarred from the argument that the 
“ tendencies” of the physiological units are derived from the in- 
herited effects of environing actions. If the conception of a 
“ first organism ” were a necessary one, the reviewer’s objection 
would be valid. If there were an “ absolute commencement ” 
of life, a definite line parting organic matter from the simplest 
living forms, I should be placed in the predicament he describes. 
But as the doctrine of Evolution itself tacitly negatives any such 
distinct separation; and as the negation is the more confirmed 
by the facts the more we know of them; I do not feel that I am 
entangled in the alleged difficulty. My reply might end here; 
but as the hypothesis in question is one not easily conceived, and 
very apt to be misunderstood, I will attempt a further elucida- 
tion of it. 
Much evidence now conspires to show that molecules of the 
substances we call.elementary are in reality compound; and that, 
by the combination of these with one another, and recombina- 
tions of the products, there are formed systems of systems of mole- 
cules, unimaginable in their complexity. Step by step, as the ag- 
gregate molecules so resulting grow larger and increase in hete- 
rogeneity, they become more unstable, more readily transforma- 
ble by small forces, more capable of assuming various char- 
acters. Those composing organic matter transcend all others in 
size and intricacy of structure ; and in them these resulting traits 
reach their extreme. As implied by its name, protein, the essen- 
tial substance of which organisms are built, is remarkable alike 
for the variety of its metamorphoses and the facility with which 
it undergoes them: it changes from one to another of its thou- 
sand isomeric forms on the slightest change of conditions. Now, 
there are facts warranting the belief that though these multitu- 
dinous isomeric forms of protein will not unite directly with one 
another, yet they admit of being linked together by other ele- 
ments with which they combine. And it is very significant that 
there are habitually present two other elements, sulphur and phos- 
phorus, which have quite special powers of holding together 
many equivalents—the one being pentatomic and the other hex- 
atomic. So that it is a legitimate supposition (justified by analo- 
gies) that an atom of sulphur may be a bond of union among 
half a dozen different isomeric forms of protein; and similarly 
with phosphorus. A moment’s thought will show that, setting HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
11 
out with the thousand isomeric forms of protein, this makes possi- 
ble a. number of these combinations almost passing the power of 
figures to express. Molecules so produced, perhaps exceeding in 
size and complexity those of protein as those of protein exceed 
those of inorganic matter, may, I conceive, be the special units be- 
longing to special kinds of organisms. By their constitution they 
must have a plasticity, or sensitiveness to modifying forces, far 
beyond that of protein ; and bearing in mind not only that their 
varieties are practically infinite in number, but that closely allied 
forms of them, chemically indifferent to one another as they must 
be, may coexist in the same aggregate, we shall see that they are 
fitted for entering into unlimited varieties of organic structures. 
The existence of such physiological units, peculiar to each 
species of organism, is not unaccounted for. They are evolved 
simultaneously with the evolution of the organisms they compose 
—they differentiate as fast as these organisms differentiate ; and 
are made multitudinous in kind by the same actions which make 
the organism they compose multitudinous in kind. This concep- 
tion is clearly representable in terms of the mechanical hypothe- 
sis. Every physicist will indorse the proposition that in each ag- 
gregate there tends to establish itself an equilibrium between the 
forces exercised by all the units upon each and by each upon all. 
Even in masses of substance so rigid as iron and glass, there goes 
on a molecular rearrangement, slow or rapid according as cir- 
cumstances facilitate, which ends only when there is a complete 
balance between the actions of the parts on the whole and the 
actions of the whole on the parts: the implication being that 
every change in the form or size of the whole necessitates some 
redistribution of the parts. And though, in cases like these, 
there occurs only a polar rearrangement of the molecules, with- 
out changes in the molecules themselves; yet where, as often 
happens, there is a passage from the colloid to the crystalloid 
state, a change of constitution occurs in the molecules themselves. 
These truths are not limited to inorganic matter: they unques- 
tionably hold of organic matter. As certainly as molecules of 
alum have a form of equilibrium, the octahedron, into which they 
fall when the temperature of their solvent allows them to aggre- 
gate, so certainly must organic molecules of each kind, no matter 
how complex, have a form of equilibrium in which, when they 
aggregate, their complex forces are balanced—a form far less 
rigid and definite, for the reason that they have far less definite 
polarities, are far more unstable, and have their tendencies more 
easily modified by environing conditions. Equally certain is it 
that the special molecules, having a special organic structure as 
their form of equilibrium, must be reacted upon by the total 
forces of this organic structure; and that, if environing actions 
lead to any change in this organic structure, these special mole- 12 
SPONTANEOUS GENERATION, AND THE 
cules, or physiological units, subject to a changed distribution of 
the total forces acting upon them will undergo modification— 
modification which their extreme plasticity will render easy. By 
this action and reaction I conceive the physiological units pecu- 
liar to each kind of organism to have been moulded along with 
the organism itself. Setting out with the stage in which protein 
in minute aggregates took on those simplest differentiations 
which fitted it for differently-conditioned parts of its medium, 
there must have unceasingly gone on perpetual readjustments 
of balance between aggregates and their units—actions and reac- 
tions of the two, in which the units tended ever to establish the 
typical form produced by actions and reactions in all antecedent 
generations, while the aggregate, if changed in form by change 
of surrounding conditions, tended ever to impress on the units a 
corresponding change of polarity, causing them in the next gen- 
eration to reproduce the changed form—their new form of equi- 
librium. 
This is the conception which I have sought to convey, though 
it seems unsuccessfully, in the Principles of Biology ; and which 
I have there used to interpret the many involved and mysterious 
phenomena of Genesis, Heredity, and Variation. In one respect 
only am I conscious of having so inadequately explained myself 
as to give occasion for a misinterpretation—the one made by the 
Westminster reviewer above referred to. By him, as by your 
own critic, it is alleged that in the idea of “ inherent tendencies ” 
I have introduced, under a disguise, the conception of “ the ar- 
chmus, vital pi’inciple, nisus formativus, and so on.” This allega- 
tion is in part answered by the foregoing explanation. That 
which I have here to add, and did not adequately explain in the 
Principles of Biology, is, that the proclivity of units of each 
order toward the specific arrangement seen in the organism they 
form is not to be understood as resulting from their own struc- 
tures and actions only, but as the product of these and the envi- 
roning forces to which they are exposed. Organic evolution 
takes place only on condition that the masses of protoplasm 
formed of the physiological units, and of the assimilable materi- 
als out of which others like themselves are to be multiplied, are 
subject to heat of a given degree—are subject, that is, to the un- 
ceasing impacts of undulations of a certain strength and period ; 
and, within limits, the rapidity with which the physiological 
units pass from their indefinite arrangement to the definite ar- 
rangement they presently assume is proportionate to the strengths 
of the ethereal undulations falling upon them. In its complete 
form, then, the conception is that these specific molecules, having 
the immense complexity above described, and having correspond- 
ently complex polarities which cannot be mutually balanced by 
any simple form of aggregation, have, for the form of aggregation HYPOTHESIS OF PHYSIOLOGICAL UNITS. 
13 
in which all their forces are equilibrated, the structure of the 
adult organism to which they belong; and that they are com- 
pelled to fall into this structure by the cooperation of the envi- 
roning forces acting on them, and the forces they exercise on one 
another—the environing forces being the source of the power 
which effects the rearrangement, and the polarities of the mole- 
cules determining the direction in which that power is turned. 
Into this conception there enters no trace of the hypothesis of an 
“ archams or vital principle; ” and the principles of molecular 
physics fully justify it. 
It is, however, objected that “ the living body in its develop- 
ment presents a long succession of differing forms ; a continued 
series of changes for the whole length of which, according to Mr. 
Spencer’s hypothesis, the physiological units must have an ‘ in- 
herent tendency.’ Could we more truly say of any thing, ‘ it is 
unrepresentable in thought ? ’ ” I reply that if there is taken into 
account an element here overlooked, the process will not be 
found “ unrepresentable in thought.” This is the element of size 
or mass. To satisfy or balance the polarities of each order of 
physiological units, not only a certain structure of organism, but 
a certain size of organism is needed; for the complexities of that 
adult structure in which the physiological units are equilibrated 
cannot be represented within the small bulk of the embryo. In 
many minute organisms, where the whole mass of physiological 
units required for the structure is present, the very thing does 
take place which it is above implied ought to take place. The 
mass builds itself directly into the complete form. This is so 
with Acari, and among the nematoid Entozoa. But among 
higher animals such direct transformations cannot happen. The 
mass of physiological units required to produce the size as well as 
the structure that approximately equilibrates them is not all 
present, but has to be formed by successive additions—additions 
which in viviparous animals are made by absorbing, and trans- 
forming into these special molecules, the organizable materials 
directly supplied by the parent, and which in oviparous animals 
are made by doing the like with the organizable materials in the 
“ food-yelk,” deposited by the parent in the same envelope with 
the germ. Hence it results that, under such conditions, the phys- 
iological units which first aggregate into the rudiment of the 
future organism do not form a structure like that of the adult or- 
ganism, which, when of such small dimensions, does not equili- 
brate them. They distribute themselves so as partly to satisfy 
the chief among their complex polarities. The vaguely-differen- 
tiated mass thus produced cannot, however, be in equilibrium. 
Each increment of physiological units formed and integrated by 
it changes the distribution of forces; and this has a double 
effect. It tends to modify the differentiations already made, 14 
SPONTANEOUS GENERATION, AND THE 
bringing them a step nearer to the equilibrating structure; and 
the physiological units next integrated, being brought under the 
aggregate of polar forces exercised by the whole mass, which 
now approaches a step nearer to that ultimate distribution of po- 
lar forces which exists in the adult organism, are coerced more 
directly into the typical structure. Thus there is necessitated a 
series of compromises. Each successive form assumed is unstable 
and transitional: approach to the typical structure going on hand 
in hand with approach to the typical bulk. 
Possibly I have not succeeded by this explanation, any more 
than by the original explanation, in making this process “ repre- 
sentable in thought.” It is manifestly untrue, however, that I 
have, as alleged, reintroduced under a disguise the conception 
of a “ vital principle.” That I interpret embryonic development 
in terms of Matter and Motion, cannot, I think, be questioned. 
Whether the interpretation is adequate, must be a matter of 
opinion; but it is clearly a matter of fact that I have not fallen 
into the inconsistency asserted by your reviewer. At the same 
time I willingly admit that, in the absence of certain statements 
which I have now supplied, he was not unwarranted in represent- 
ing my conception in the way that he has done. 
But, while I consider that what your reviewer has said on 
these two essential points falls within the limits of legitimate 
criticism, I do not consider that he is justified in much that he 
says by implication respecting my general views. 
In the first place, he conveys a totally wrong idea of the mode 
of interpretation he criticises. He gives his readers no concep- 
tion of the immense extensions which modern science has made 
of the “ mechanical theory,” now applied to the solution of all 
physical phenomena whatever; but he has deliberately restricted 
its applications in a way that produces an appearance of difficulty 
where no difficulty exists. The common uses of the words “ me- 
chanical ” and “ mechanist ” are such as inevitably call up in all 
minds the notions of visible masses of matter acting on one an- 
other by measurable forces and producing sensible motions. In 
the absence of explanations or illustrations serving to enlarge the 
conception thus suggested, so as to bring within it the oscilla- 
tions of the molecules of matter, and the undulations of the mole- 
cules of ether pervading all space, even the cultivated reader 
must carry with him an extremely crude and narrow idea of the 
“ mechanist theory,” and cannot fail to be struck with the seem- 
ing absurdity of interpreting vital phenomena in mechanical 
terms. But the reviewer says nothing to prevent misconceptions 
so arising. He gives no hint that heat, light, and electricity, 
are now all recognized as “ modes of motion ; ” and that most of 
their phenomena are mechanically interpreted, while the rest are 
regarded as mechanically interpretable. He does not explain HYPOTHESIS OF PHYSIOLOGICAL EXITS. 
15 
that the “ mechanist ” theory in its comprehensive form embraces 
actions such as those by which variations in the solar spots cause 
variations in our magnetic needles, and actions such as those 
through which Sirius tells us what substances are contained in 
his atmosphere. True, he makes a passing reference to chemical 
changes as being included by me under the conception of me- 
chanical ; but he leaves this as a dead statement quite unintelli- 
gible to the general reader; and in the typical example he gives 
of my mode of interpretation (the development of vertebras by 
transverse strains) he deliberately excludes the physio-chemical 
and chemical actions which I imply as cooperating, and describes 
me as attributing the effects entirely to the pressures and ten- 
sions caused by muscular movements ! (See p. 408.) Instead 
of the developed ideas of Matter and Motion everywhere implied 
throughout the Principles of Biology, the reviewer leads every 
one to suppose that I bring to bear on biological problems noth- 
ing beyond the vulgar ideas of Matter and Motion, and leaves me 
responsible for the ludicrous incongruity ! 
That, however, which I regard as most reprehensible in his 
criticism is the way in which he persists in representing the /Sys- 
tem of Philosophy I am working out as a materialistic system. 
Already he has once before so represented it, and the injustice 
of so representing it has been pointed out. He knows that I 
have repeatedly and emphatically asserted that our conceptions 
of Matter and Motion are but symbols of an Unknowable Reality; 
that this Reality cannot be that which we symbolize it to be; 
and that, as manifested beyond consciousness under the forms of 
Matter and Motion, it is the same as that which, in consciousness, 
is manifested as Feeling and Thought. Yet he continues to de- 
scribe me as reducing every thing to dead mechanism. If his 
statement on pp. 383-4 has any meanig at all, it means that there 
exists some “ force operating ah extra f some “ external power ” 
distinguished by him as “ mechanical,” which is not included in 
that immanent force of which the universe is a manifestation; 
though whence it comes he does not tell us. This conception he 
speaks of as though it were mine ; making it seem that I ascribe 
the moulding of organisms to the action of this “ mechanical ” 
“ external power,” which is distinct from the Inscrutable Cause 
of things. Yet he either knows, or has ample means of know- 
ing, that I deny every such second cause : indeed, he has himself 
classed me as an opponent of dualism. I recognize no forces 
within the organism, or without the organism, but the variously- 
conditioned modes of the universal immanent force; and the 
whole process of organic evolution is everywhere attributed by 
me to the cooperation of its variously-conditioned modes, internal 
and external. That this has been all along my general view, is 
clearly shown in the closing paragraph of First Principles, where 
I have said— 16 
SPONTANEOUS GENERATION, ETC. 
“ A Power of which the nature remains forever inconceivable, and to which 
no limits in Time or Space can be imagined, works in us certain effects. These 
effects have certain likenesses of kind, the most general of which we class to- 
gether under the names of Matter, Motion, and Force ; and between these effects 
there are likenesses of connection, the most constant of which we class as laws 
of the highest certainity. • Analysis reduces these several kinds of effect to one 
kind of effect; and these several kinds of uniformity to one kind of uniformity. 
And the highest achievement of Science is the interpretation of all orders of 
phenomena, as differently-conditioned manifestations of this one kind of effect, 
under differently-conditioned modes of this one kind of uniformity. But, when 
Science has done this, it has done nothing more than systematize our experi- 
ence ; and has in no degree extended the limits of our experience. We can say 
no more than before, whether the uniformities are as absolutely necessary, as 
they have become to our thoughts relatively necessary. The utmost possi- 
bility for us, is an interpretation of the process of things as it presents itself to 
our limited consciousness; but, how this process is related to the actual pro- 
cess, we are unable to conceive, much less to know. Similarly, it must be re- 
membered that, while the connection between the phenomenal order and the 
ontological order is forever inscrutable, so is the connection between the con- 
ditioned forms of being and the unconditioned form of being forever inscruta- 
ble. The interpretation of all phenomena in terms of Matter, Motion, and 
Force, is nothing more than the reduction of our complex symbols of thought 
to the simplest symbols ; and when the equation has been brought to its lowest 
terms the symbols remain symbols still. Hence the reasonings contained in 
the foregoing pages afford no support to either of the antagonist hypotheses 
respecting the ultimate nature of things. Their implications are no more ma- 
teralistic than they are spiritualistic ; and no more spiritualistic than they are 
materialistic. Any argument which is apparently furnished to either hypoth- 
esis is neutralized by as good an argument furnished to the other. The Ma- 
terialist, seeing it to be a necessary deduction from the law of correlation that 
what exists in consciousness under the form of feeling is transformable into an 
equivalent of mechanical motion, and by consequence into equivalents of all the 
other forces which matter exhibits, may consider it therefore demonstrated 
that the phenomena of consciousness are material phenomena. But the Spirit- 
ualist, setting out with the same data, may argue with equal cogency, that if 
the forces displayed by matter are cognizable only under the shape of those 
equivalent amounts of consciousness which they produce, it is to be inferred 
that these forces, when existing out of consciousness, are of the same intrinsic 
nature as when existing in consciousness ; and that so is justified the spiritual- 
istic conception of the external world, as consisting of something essentially 
identical with what we call mind. Manifestly, the establishment of correlation 
and equivalence between the forces of the outer and the inner worlds may be 
used to assimilate either to the other; according as we set out with one or 
other term. But he who rightly interprets the doctrine contained in this work 
will see that neither of these terms can be taken as ultimate. He will see that- 
though the relation of subject and object renders necessary to us these anti- 
thetical conceptions of Spirit and Matter, the one is no less than the other to be 
regarded as but a sign of the Unknown Reality which underlies both.” 
This is the conception which jour reviewer continues to speak 
of as “ mechanical ” and “ mechanist,” without giving his readers 
any suspicion of the qualified sense in which only these words 
can be applied. If he thinks that by doing this he has repre- 
sented the conception with fairness, or with any approach to fair- 
ness, I cannot agree with him. 
I am, sir, yours, etc., 
HERBERT SPENCER. 
London, December 5, 1868. SPENCEB’S ■ 
SYSTEM OF PHILOSOPHY. 
The attention of the reading public is invited to this great 
work of Mr. Herbert Spencer, now in course of regular republi- 
cation in this country. 
When, in 1860, he issued the prospectus of a comprehensive 
philosophical scheme in which it was proposed to embrace the 
subjects of Life, Mind, Society, and Morality in one system of 
scientific principles, the project was naturally looked upon by 
many as chimerical. The term “ Philosophy ” had been so long 
applied to speculations upon remote and transcendental ques- 
tions yielding only empty and discordant results, that a strong 
prejudice existed against any thing calling itself by that name ; 
so that the announcement of a New Philosophical System was 
looked upon, not as promising a contribution to real knowledge, 
but only as a fresh display of futile ingenuity in an exhausted 
and a hopeless field. It was, besides, thought impossible to re- 
duce such diverse subjects to any .thing like a philosophical unity 
of treatment; while the task, even if possible, was held to be 
beyond the power of any single mind to accomplish. 
Uninfluenced by these considerations, Mr. Spencer went for- 
ward with his undertaking; and that he has not entered upon the 
pursuit of a chimera, but upon the solution of a problem which, 
though vast, is still practicable, will be apparent when we con- 
sider his point of view. By “ Philosophy ” he understands the 
deepest explanation of the universal order at which man can 
arrive. Renouncing all hope of passing beyond phenomena and 
their laws, he proposes, as the task of Philosophy, the deter- 
mination of those broadest principles which are disclosed within 
the phenomenal order of the universe. The several sciences give 
us separate explanations of the divisions of Nature; Philosophy 2 
seeks by combining these explanations to arrive at universal 
principles. It is the tendency of all science to disclose a unity 
in the method of Nature; Philosophy thus becomes an expres- 
sion of that unity, and may hence be defined as the highest 
unification of knowledge. Here is a definite, legitimate, and 
fruitful field of inquiry. 
The largest principle of action in the world of natural phe- 
nomena Mr. Spencer found shadowed forth as an onward move- 
ment from one order of things to another—a kind of vague, 
progressive unfolding. The latest astronomy, for example, de- 
clares that the solar system has been evolved from a nebulous 
origin. So geology affirms that the earth was once a molten 
mass of chaotic material. We are familiar with the growth of 
plants from seeds; of animals from ova; and with the decay and 
disappearance of living forms. Mind also has its unfolding and 
its decline; while the arts of civilization and the changes of 
social life have been progressive. But, although vague analogies 
may have been obscurely perceived among those remote and 
widely-diverse phenomena, nothing like a common and clearly- 
defined law, binding them together, was at all suspected. The 
first step in this direction was taken by the eminent natu- 
ralist Yon Baer early in the century. He obtained a partial 
glimpse of the ultimate principle of growth in the world of life, 
and formulated his conception into a law of organic development. 
Mr. Spencer took up the inquiry at this point. He showed that 
Von Baer’s conception of the principle was incomplete, and he 
worked it into greater fulness and clearness, determining its ele- 
ments, limitations, and causes. He discovered also that the law 
of organic development, when analyzed and defined with pre- 
cision, turned out to be equally applicable to all orders of phe- 
nomena, and was in fact nothing less than a universal Law of 
Evolution. 
The view thus arrived at had a new and startling signifi- 
cance. The conception of a universe in evolution — of astro- 
nomic systems, of our planet, of the spheres of life, mind, and 
society, governed in all their changes by one demonstrable rule 
of action, created an epoch in the advance of thought. A 
new point of departure was reached: the highest problems of 
human inquiry were reset in new lights and new relations, and 3 
a new Philosophy of the world became not only possible, but in- 
evitable. Mr. Spencer grasped the full import of the situation, 
and entered unhesitatingly upon the great task of working out 
the new views into a coherent and all-comprehensive system of 
thought. Personally the circumstances were unpropitious. With 
very imperfect health, without means, and without a publisher to 
relieve him of business responsibilities, he closed with this for- 
midable undertaking, and, in carrying it on under these crushing 
difficulties, he has exhibited a moral intrepidity in admirable 
keeping with the intellectual grandeur of the task. 
The development of the system is now considerably ad- 
vanced. We have the foundation volume, “First Principles,” de- 
voted to an elucidation of the Law of Evolution. Next follows 
the “ Principles of Biology,” in two volumes, in which that law is 
systematically applied to the phenomena of life. Based upon 
the Biology is the third division, the “ Principles of Psychology,” 
of which two completed parts, the Data of Psychology, and the 
Inductions of Psychology, have been lately republished. Thus 
a sufficiently large portion of the scheme is finished to enable 
us to judge of its claims; and we do not hesitate to say that, 
in the whole range of scientific and philosophic literature, noth- 
ing more clear, comprehensive, original, and profound, has yet 
appeared than the parts of Spencer’s Philosophy which are now 
before the world. The most advanced thinkers in the leading 
countries of Europe have recognized its claims, and justify the 
declaration that it is beyond doubt the most important intellec- 
tual enterprise of our time. If this statement is objected to, as 
only an individual opinion, it is easily reenforced by authorities 
that will not be questioned. 
As an indication of tlie position which Mr. Spencer has at- 
tained on the Continent, it may be mentioned that all his works 
are now being translated into Russian and published at St. 
Petersburg, by M. Thieblin, and that three translators, all Profess- 
ors of Philosophy, are occupied in rendering them into French. 
Dr. Cazelles has translated “ First Principles,” and is now engaged 
upon the “ Biology; ” Prof. Ribot, of the Lycee Imperial, Laval, 
is translating the “ Principles of Psychology; ” and Prof. Pethore, 
of the Lycee Imperial, Angouleme, has translated the “ Edu- 
cation” and the “Classification of the Sciences.” 4 
It may be further stated that Mr. Spencer’s philosophical 
works have been adopted as text-books for the science classes 
in the University of Oxford, and questions upon them set for 
examination of students. 
We cannot here offer any recent opinions of the English 
press on Mr. Spencer’s System of Philosophy, for the sufficient 
reason that he has of late sent out no copies of his work for re- 
view.* The misstatements made by critics, who were either too 
idle to read his books or incompetent to form estimates of them, 
he had from the beginning taken as things to be expected and 
endured. Not long ago, however, he found, from personal testi- 
mony, that even those most interested in some of the topics 
treated by him had, for years, been deterred from looking at his 
works by the false impressions which press-notices had given to 
them. On learning this, he concluded that it would be best no 
longer to give occasion for these misleading criticisms. Neither 
of his last two volumes has been issued to the newspapers or the 
literary journals, and his English publishers have now a standing 
order not to send out for review any future work of his. 
But, though no indorsement by anonymous critics can be 
cited, we may cite indorsements of much greater weight; the 
publicly-expressed opinions of well-known men, thoroughly com- 
petent to judge. The reader’s attention is asked to the follow- 
ing extracts from works published by authors whose names are 
given : 
* Nevertheless, incidental references constantly occur in the leading periodicals, 
which show the position Mr. Spencer has won in the world of thought. A late number 
of the Saturday Review, for example, has the following: “ If we were to give our own 
judgment, we should say that, since Newton, there has not in England been a philoso- 
pher of more remarkable speculative and systematizing talent than (in spite of some 
errors and some narrowness) Mr. Herbert Spencer.”— London Saturday Review, Feb- 
ruary 6, 1869. 
Again, an able writer in the last number of the Westminster Review, in criticising 
Lecky’s “History of Morals,” thus speaks of Mr. Spencer: “Before entering on the 
discussion of his views, we cannot refrain from offering our tribute of respect to one 
who, whether for the extent of his positive knowledge, or for the profundity of his 
speculative insight, has already achieved a name second to none in the whole range of 
English philosophy, and whose works will worthily sustain the credit of English thought 
in the present generation.” 
Again, referring to Mr. Spencer’s application of the Principles of Evolution to ethi- 
cal philosophy, the writer says: “ It appears to us that, even in its present stage, this 
theory of the progressive development of moral sentiments in the hereditary conscience 
of the race is the greatest advance which has been made in ethereal speculation since 
the time of Hartley.”— Westminster Review, October, 1869. “Mo such defect can be charged against the other writer wThom I am now to 
name—Mr. Herbert Spencer. Of all our thinkers he is the one who, as it ap- 
pears to me, has formed to himself the largest new scheme of a systematic phi- 
losophy, and, in relation to some of the greatest questions of Philosophy in their 
most recent forms, as set or reset by the last speculations and revelations of 
science, has already shot his thoughts the farthest. He both works out his 
Philosophy physiologically and psychologically from the centre, and—what seems 
to me an eminent merit in relation to the intellectual needs of the time—surveys 
it and contemplates it from the circumferance cosmologieally. Indeed, I should 
say that he is the British thinker who has most distinctly realized the absolute 
necessity that Philosophy lies under, of dealing with the total cosmological con- 
ception as well as with the mere psychical or physiological organism (and this 
from the demonstrable inter-relatedness of both), if it would grasp all the pres- 
ent throbbings of the speculative intellect. His writings take for granted this 
necessity, and make it plainer than it would otherwise be. Nowhere else are 
the various sciences so fished for generalizations that may come together as a 
whole to help in forming a Philosophy. Nowhere else, at all events, is there 
a more beautiful and fearless exposition of some of those recent scientific no- 
tions which I spoke of in the last chapter as affecting our views of metaphysical 
problems. There are parts of Mr. Spencer’s waitings, occupied with such ex- 
positions, which, from sheer scientific clearness, and adequacy of language to 
the matter, have all the effect of a poem. If even only for such renderings of 
high scientific conceptions, on the chance of their somehow taking possession 
of the popular soul, and uniting there to rectify previous forms of thought, he 
would deserve honorable recognition. 
“ But Mr. Spencer does not stop short in the character of an interpreter be- 
tween Science and Philosophy, handing on the conceptions of Science to that 
congress of all the Powers, where they are to be adjusted and take effect. He 
assumes the work of the philosopher proper. He seeks to enmesh the physical 
round of things, as Science now orbs it to the instructed imagination, within a 
competent Metaphysic; he desires to fix in the centre a competent Psychology, 
consistent with this Metapliysic, and yet empirically and physiologically educed; 
and he would fill up the interior, or what of it the physical sciences leave void, 
with a competent Ethics, a competent Jurisprudence, a competent ./Esthetics, a 
competent Science of Government and Politics. 
“In this great work he is still engaged: and it will not perhaps be till the 
whole is accomplished that there will be the means of determining either the 
sufficiency of Mr. Spencer’s philosophy for the higher practical purposes of phi- 
losophy, or its exact intellectual relations to previous systems. Already, in con- 
sequence both of the decisiveness of his views and the variety of interesting 
subjects over which they extend, Mr. Spencer, more than any other systematic Brit- 
ish thinker save Mill, has an avowed following both here and in America; and, 
if any individual influence is visibly encroaching on Mill’s in this country, it is 
his. For my own part, believing that no type of man ought to be more pre- 
cious to a nation than a resolute systematic thinker, and believing Mr. Spencer 
to be a very Jiigh specimen of this type, I anticipate nothing but good—nothing, 
at least, but a clearing away of the bad—from what he has already done, or may 
yet do.”—Recent British Philosophy, Chapter iv. 
Prof. Masson, of the University of Edinburgh. 
Mr. John Stuart Mill. 
“ The last extract is from Mr. Herbert Spencer, whose Principles of Psy- 
chology, in spite of some doctrines which he holds in common with the intuitive 
school, are, on the whole, one of the finest examples we possess of the Psycho- 
logical method in its full power.”—Mill’s Hamilton, Chapter xiii.—“ One of the 
acutest Metaphysicians of modern times.”—Ibid., Chapter ii. 
“ Mr. Spencer is one of the small number of persons who, by the solidity and encyclopaedical character of their knowledge, and their power of coordination 
and concatenation, may claim to be peers of M. Comte, and entitled to a vote in 
the estimate of him.”—Mill's Review of Comte.—“ One of the most vigorous as 
well as boldest thinkers that English speculation has yet produced.”—Ibid. 
M. Laugel. 
“ The great work on Philosophy by Herbert Spencer, whom I would style 
the last of English Metaphysicians. In the midst of universal indifference, Mr. 
Spencer remained steadily attached to his philosophical studies, displaying all 
that heroic courage and that rare independence indispensable to those who de- 
vote themselves to toilsome researches which at best only recompense the stu- 
dent with a few obscure and isolated suffrages. If Mr. Spencer, with his talents, 
his fertility of genius, and the almost encyclopaedic variety of knowledge of 
which his writings furnish the proof, had chosen to follow the beaten path, noth- 
ing would have been more easy than for him to secure all those honors of which 
English society is so prodigal to those who serve her as she wishes to be served. 
He preferred, however, with a noble and touching self-denial, to put up with pov- 
erty, and, what is still more difficult, with obscurity. But he deserves more than 
vain assurances of sympathy: we must not merely admire his fidelity to profit- 
less studies; his work itself merits the individual attention of all friends of Phi- 
losophy.”—Revue des Deux Mondes, of February 15, 1864. 
“ Those who hold the doctrine of Evolution (and I am one of them) con- 
ceive that there are grounds for believing that the world, with all that is in it 
and on it, did not come into existence in the condition in which we now see it, 
nor in any thing approaching that condition. 
“ On the contrary, they hold that the present conformation and composition 
of the earth’s crust, the distribution of land and water, and the infinitely diversi- 
fied forms of animals and plants which constitute its present population, are 
merely the final terms in an immense series of changes which have been brought 
about, in the course of immeasurable time, by the operation of causes more or 
less familiar to those which are at work at the present day. 
“ Perhaps this doctrine of Evolution is not maintained consciously and in its 
logical integrity by a very great number of persons. The only complete and 
systematic statement of the doctrine with which I am acquainted is that con- 
tained in Mr. Herbert Spencer’s ‘ System of Philosophy ; ’ a work which should 
be carefully studied by all who desire to know whither scientific thought is tend- 
ing.”—Lecture before the Royal Institute of Great Britain. 
Prof. T. II. Huxley, F. R. S., LL. D. 
James McCosh, D. D., LL. D. 
“ In the new edition of his ‘ Intuitions of Mind,’ Dr. McCosh dovotes a chap- 
ter to Spencer’s Philosophy. But, ‘ great as are the author’s intellectual pow- 
ers,’ he believes that its success is beyond the reach of this ‘ giant mind,’ and 
indeed beyond the present possibility of science. Yet he observes: ‘This in 
regard to his theory as a whole; but his bold generalizations are always sugges- 
tive, and some may in the end be established as the profoundest laws of the 
knowable universe.’ ” 
Joseph D. Hooker, F. B. S., LL. D. 
“ Another instance of successful experiment in Physiological Botany is Mr. 
Herbert Spencer’s observations on the circulation of the sap and the formation 
of wood in plants. As is well known, the tissues of our herbs, shrubs, and trees, 
from the tips of their roots to those of their petals and pistils, are permeated by 
tubular vessels. The functions of these have been hotly disputed, some physi- 
ologists affirming that they convey air, others fluids, others gases, and still others 
assigning to them far-fetched uses, of a wholly different nature. By a series of 
admirably contrived and conducted experiments, Mr. Spencer has shown not 7 
only that these vessels are charged at certain seasons of the year with fluid, but 
that they are intimately connected with the formation of wood. He further inves- 
tigates the nature of the special tissues concerned in this operation, and shows 
not merely how they may act, but to a great extent how they do act. As this 
paper will, I believe, be specially alluded to by the President of the Biological 
Section, 1 need dwell no further on it here, than to quote it as an example of 
what may be done by an acute observer and experimentalist, versed in physics 
and chemistry, but, above all, thoroughly instructed in scientific methods.”— 
Inaugural Address at Meeting of British Association, 1868. 
“ One of our deepest thinkers, Mr. Herbert Spencer.”—Ibid. 
George Henry Lewes. 
“ This last-named writer (Mr. Spencer) is now daily rising into wider influ- 
ence. .... Even antagonists are compelled to admit the force and clear- 
ness of his genius, and the extent and profundity of his scientific knowledge. It 
is questionable whether any thinker of finer calibre has appeared in our country, 
although the future alone is to determine the position lie is to assume in history. 
. . . . He alone, of all British thinkers, has organized a philosophy.”— 
History of Philosophy, vol. ii., p. 653. 
“ Among modern English psychologists the author to whom I have been most 
indebted in this work is Mr. Herbert Spencer ; more especially to the very able 
analysis which he has given of the process of reasoning in its qualitative and 
quantitative forms. So far as I have touched upon the theory of reasoning at 
all, I have followed to a large extent the pathway that he has pointed out, and 
which appears to me the most successful analysis which this subject has yet re- 
ceived in our own country.”—Outlines of Mental Philosophy. 
“ Mr. Spencer is equally remarkable for his search after first principles; for 
his acute attempts to decompose mental phenomena into their primary elements ; 
and for his broad generalizations of mental activity, viewed in connection with 
Nature, instinct, and all the analogies presented by life in its universal aspects.” 
—Medico- Chirurgical Review. 
J. D. Morrell, LL. D. 
“ I have read Herbert Spencer through, and some of the Essays twice. His 
volume on Education will do much to change the opinions of the civilized world. 
I hope it will be widely read here and in England. As to the worth of knowl- 
edge, he is very strong; here he and I are aiming at the same thing. I did not 
expect to see in my day one with whose views I could so sincerely sympathize. 
He speaks to the common-sense of humanity, and hates sham; and he will 
triumph, though it will take some time first.”—Life of Dr. Wayland, vol. ii., p. 
294. 
Dr. Francis Wayland, late President of Brown University. 
“ An author who is both extensively and profoundly versed in science, and 
who writes, on all the subjects which he handles, with great power, equally of 
observation, abstraction, and generalization: for such is Herbert Spencer, 
author of a ‘System of Philosophy,’ now in course of publication.”—Mind: its 
Powers and Capacities, p. 9. 
J. Gr. Macvicat, D. D. 
The most striking feature of Mr. Spencer as a philosopher, is the consum- 
mate degree in which he unites the power of abstract thought with the knowl- 
edge of scientific conclusions, lie is as keen an analyst as is known in the his- 
tory of Philosophy: I do not except either Aristotle or Kant, whom he greatly 
resembles in the trait to which I allude lie is familiar with the whole 
domain of the universe, whether that of consciousness or of observation. His out- 
sight, so to speak, is as keen as his insight. No abstraction is too delicate and 
subtle for his mental grasp.”—Letter to the New York Tribune. 
Mr. George Ripley. WORKS OF HERBERT SPENCER, 
PUBLISHED BY 
D. APPLETON AND COMPANY. 
SYSTEM OF PHILOSOPHY. 
I.—FIRST PRINCIPLES. 
(New and Enlarged Edition.) 
Part I.—The Unknowable. 
Part II.—Laws of the Knowable. 
559 pages. Price, $2.50 
II.—THE PRINCIPLES OF BIOLOGY.—VOL. I. 
Part I.—The Data of Biology. 
Part II.—The Inductions of Biology. 
Part III.—The Evolution of Life. 
475 pages. Price, $2.50 
PRINCIPLES OF BIOLOGY.—VOL. II. 
Part IV.—Morphological Development. 
Part V.—Physiological Development. 
Part VI.—Laws of Multiplication. 
565 pages. Price, - $2.50 
III.—THE PRINCIPLES OF PSYCHOLOGY. 
Part I.—The Data of Psychology. 
144 pages. Price, $0.75 
Part II.—The Inductions of Psychology. 
146 pages. Price, $0.75 
MISCELLANEOUS. 
I.—ILLUSTRATIONS OF UNIVERSAL PROGRESS. 
Thirteen Articles. 451 pages. Price, - $2.50 
II.—ESSAYS: 
Moral, Political, and 
Ten Essays. 386 pages. Price, ...... $2.50 
III.—SOCIAL STATICS: 
Or the Conditions Essential to Human Happiness Specified, and the 
First of them Developed. 
523 pages. Price, - $2.50 
IV.—EDUCATION: 
Intellectual, Moral, and Physical. 
283 pages. Price, $1.75 
V—CLASSIFICATION OF THE SCIENCES. 
50 pages. Price, ... . ..... $0.25 
VI.—SPONTANEOUS GENERATION, &c. 
16 pages. Price, $0.25 Works of Herbert Spencer published by D. Appltti n & Co. 
The Philosophy of Herbert Spencer. 
THE 
PRINCIPLES OF BIOLOGY 
Vol. I. 475 pag-es. (Now in press.) 
CONTENTS: 
Part I.—The Data of Biology. 
I Organic Matter.—II. The actions of Forces on Organic Matter.—III. The 
re-actions of Organic Matter on Forces.—IV. Proximate Definition of 
Life.—V. The Correspondence between Life and its Circumstances.— 
VI. The Degree of Life varies as the Degree of Correspondence.— 
VII. The Scope of Biology. 
Part II.—The Inductions of Biology. 
1. Growth.—II. Development.—III. Function.—IV. Waste and Repair.— 
V. Adaptation.—VI. Individuality.—VII. Genesis.—VIII. Heredity.— 
IX. Variation.—X. Genesis, Heredity, and Variation—XI. Classifica- 
tion.—XII. Distribution. 
Part III.—The Evolution of Lera 
I. Preliminary.—II. General Aspects of the Special-creatiou-hypothesis.— 
III. General Aspects of the Evolution-hypothesis.—IV, The Arguments 
from Classification.—V. The Arguments from Embryology.—VI. The 
Arguments from Morphology.—VII. The Arguments from Distribution. 
—VIII. How is Organic Evolution caused?—IX. External Factors.— 
X. Internal Factors.—XL Direct Equilibration.—XII Indirect Equili- 
bration.—XIII. The Cooperation of the Factors.—XIV. The Converg- 
ence of the Evidences. 
All these works are rich in materials for forming intelligent opinions, even where 
we are unable to agree with those put forth by the author. Much may be learned from 
.hem in departments in which our common Educational system is very deficient. The 
active citizen may derive from them accurate systematized information concerning his 
highest duties to society, and the principles on which they are based. He may gain 
clearer notions of the value and bearing of evidence, and be better able to distinguish 
between facts and inferences. He may find common things suggest! ye of wiser thought 
—nay, we will venture to say of truer emotion—than before. By gi ving us fuller reali- 
zations of liberty and justice his writings will tend to increase our self-reliance in the 
treat emergency of civilization to which we have been summoned — Atlantic MrmthU In Due Volume, 8v:Cloth. Pritc Six Dollars. 
TIIE 
PRINCIPLES OF PSYCHOLOGY. 
BY 
HERBERT SPENCER, 
OPINIO VS OF TIIE PRESS. 
-— Mr. Herbert Spencer, of whose able and various writings, bis “Princi- 
ples of Psychology ” is one of tin; ablest.—Edinburgh Review. 
We have to notice the very a ole work of Mr. Herbert Spencer on Psycholo- 
gy, to which, however, we fear justice cannot be clone within the utmost space 
that we can assign to it.— Went minster Review. 
It exhibits original thought, vast range of scientific knowledge, logical 
powers of a high order, and great abilities as a writer.— British Quarterly Re- 
view. 
Thus, by far the most able recent writer of this school, Mr. Herbert 
Spencer National1 Review. 
We may say, indeed, (witlio t by any means endorsing all the individual 
' results arrived at,) that, in our apprehension, this well-studied and deeply- 
philosophie volume presents o; the whole one of the most vigorous attempts 
which has yet been made in oar country to place mental philosophy upon a 
broad and positive basis.—British and Foreign Medico-Ohirurgical Review. 
It is the production of a bold and vigorous thinker, and is marked through- 
out by keenness and subtlety of thought, closeness of reasoning, and singular 
force and clearness of language.—New Quarterly Review. 
What Schwann did for Physiology, Herbert Spencer has done for Psychol- 
ogy It is not a work to be fathomed at a glance, but whoever will 
patiently read and consider it, will feel that he has here a guide of singular 
power and clearness, or an antagonist such as he has not grappled with since 
Spinoza.— Leader. 
It is new in its leading ideas, new in conception, new in illustration, while 
it is nevertheless a continuation and development of lines of thought which 
science has gradually been preparing For vigour of mind and logical 
consistency, there are fewwoiks which we could place above it.—Saturday 
Review. 
Though we conceive Mr. Spencer's speculations audacious and unfounded, 
we are bound to say of his book, that it displays a talent not often equalled ; 
and that, in the second part especially, his analytical power is of the highest 
order. The Sensationalist theory of the genesis of knowledge has not of late 
received so powerful an accession, and it will require more subtlety and strength 
to refute his conclusions on the origin of our notions of matter and its proper- 
ties than any living Idealist writer has as yet displayed.—Spectator. 
New York: D. Appleton and Company