358 
NATURE 
[Mar. 13, 1873 
history that some propositions the negation of which was 
at one time inconceivable are now known to be false. 
His examples are—that in sunrise and sunset, it is the 
sun that moves; that gravitation cannot act through 
space absolutely void ; and that there cannot exist anti- 
podes—men sticking on by their feet to the under side of 
the earth. For the truth of each of these propositions 
Mr. Mill thinks that our forefathers had the warrant of 
what Mr. Spencer calls the Universal Postulate. “To this 
criticism of Mr. Mill,” says Mr. Spencer, referring to the 
first and last of these propositions, “my reply is that the 
propositions erroneously accepted because they seemed 
to withstand the test, were complex propositions to which 
the test is inapplicable.” Unfortunately, in his anxiety 
to ‘leave no possibility of misapprehension,” Mr. 
Spencer mentioned, among other things, that we cannot 
by simple comparison of two states of consciousness 
know that the square of the hypothenuse of a right- 
angled triangle equals the sum of the squares of the 
other two sides. The strange result has been that Mr. 
Mill has, we cannot help thinking, fallen into a complete 
misapprehension of his meaning. In the eighth edition 
of his Logic, Mr. Mill has had the opportunity of reply- 
ing to Mr. Spencer’s argument as it stands in the volu me 
before us. He there says: “It is but just to give Mr. 
Spencer’s doctrine the benefit of the limitation he claims— 
viz. that it is only applicable to propositions which are 
assented to on simple inspection, without any intervening 
media of proof. . . . But in all the three cases which I 
have just cited (those mentioned), the inconceivability 
seems to be apprehended directly ; no train of argument 
is needed, as in the case of the square of the hypo- 
thenuse, to obtain the verdict of consciousness on the 
point.” We submit that the quality of being “ assented 
to on simple inspection, without any intervening media of 
proof” is not the distinguishing characteristic of what 
Mr, Spencer calls a simple proposition. The propositions 
that can be properly brought to the test of the inconceiv- 
ableness of their negation are not such as are assented to 
on simple inspection, but such as “ are not further decom- 
posable.” Until this misconception on the part of Mr. 
Mill furnished conclusive evidence to the contrary, we 
were inclined to think that here, as elsewhere, Mr, 
Spencer had been needlessly tedious in stating and re- 
stating, illustrating and re-illustrating hismeaning. That 
after all Mr. Mill should have so completely missed the 
true nature of his distinction of propositions into simple 
and complex is very remarkable. Had not Mr. Spencer 
declared that the propositions in dispute were examples 
of what he considered complex propositions? There is 
no intervening media of proof when we automatically 
interpret our sensations of sight into such a cognition as 
—“There is an old man.” Yet this is one of the proposi- 
tions tediously analysed by Mr. Spencer, “to show dis- 
tinctly the number of propositions included in an ordinary 
proposition which appears simple. Again, “On a cold 
winter’s night a gas-light seen through the window of a 
cab, or a light in a shop looked at through a pane that 
has been much rubbed, is surrounded by a halo. Who- 
ever examines will see that this halo is caused by 
scratches on the glass, the curves of which are arcs of 
circles having the light for their centre. The proposition 
which expresses the result of his observation, and seems 
to assert no more than the result of his observation, is 
that on the part of the glass through which he looks the 
scratches produced by rubbing are arranged concentri- 
cally with the light.” Included ip this apparently simple 
proposition, however, is this other—“ that there does not 
exist on the same spot scratches otherwise arranged, 
immeasurably exceeding in number the concentric 
scratches.” The truth is that “the scratches on any part 
of the glass have no concentric arrangement at all, but 
run in countless directions with multitudinous curva- 
tures.” The propositions in question obviously belong to 
this class. In the assertion, the sun moves from east to 
west, there is included the other proposition—the earth 
does not revolve on its axis from west to east. We 
scarcely think that Mr. Mill will assert that any human 
being ever found it impossible to conceive, in Mr. Spencer’s 
sense, that a sphere should so revolve. Thus far, then, 
we are bound to say that Mr. Spencer’s argument remains 
intact. 
With regard to gravitation we cannot do better than 
quote the note in which Mr. Mill replies to Mr. Spencer 
on this point :— 
“In one of the three cases, Mr. Spencer, to my no 
small surprise, thinks that the belief of mankind ‘ cannot 
be rightly said to have undergone’ the change I allege. 
Mr. Spencer still thinks we are unable to conceive gravi- 
tation acting through empty space. ‘If an astronomer 
vowed that he could conceive gravitative force as exercised 
through space absolutely void, my private opinion would 
be that he mistook the nature of conception. Conception 
implies representation. Here the elements of the repre- 
sentation are the two bodies and an agency by which 
either effects the other. To conceive this agency is to 
represent it in some terms derived from our experiences— 
that is from our sensation. As this agency gives us no 
sensations, we are obliged (if we try to conceive it) to use 
symbols idealised from our sensations—imponderable 
units forming a medium.’ If Mr. Spencer means that the 
action of gravitation gives us no sensations, the assertion 
is one than which I have not seen, in the writings of 
philosophers, many more startling. What other sensa- 
tion do we need than the sensation of one body moving 
towards another? ‘The elements of the representation 
are not two bodies and an ‘ agency,’ but two bodies and 
an effect ; viz. the fact of their approaching one another. 
If we are able to conceive a vacuum, is there any diffi- 
culty in conceiving a body falling to the earth through 
itt 
We are compelled to say that Mr. Mill could not have 
been much more surprised at Mr. Spencer’s statement 
than we are at his answer. What was it that Newton 
could not conceive, but which, Mr. Mill says, we have no 
difficulty in conceiving? Was “Newton incapable of 
forming a mental representation of “one body moving 
towards another ?”—an experience that in common with 
everybody else, he had hundreds of times every day of 
his life. No. To put it in plain rough language, he was 
unable to conceive how one body could move another 
without in some way pushing or pulling at it. Hence, 
when he tried to represent in thought the action of the 
sun upon the earth he found it necessary to imagine a 
medium—an unbroken line of physical connection be- 
tween the two bodies. Have we got beyond Newton in 
this respect? or is it not rather, as Mr. Spencer says, 
that our scientific men have simply “ given up attempting 
to conceive how gravitation results.” Nay, are there not 
