134 
OUR PHYSICAL BELIEFS. 
Junk, 1889. 
these premises we test in like manner, for if the negation be 
conceivable, the argument is invalid and falls to the ground. 
It is mainly over this question of conceivability and incon¬ 
ceivability the noise of the strife is heard. 
A student of philosophy, carefully watching every step of 
his argument and checking it by this method, may be 
interrupted and disconcerted by someone saying, “ But the 
negation of your assumption, which you say is inconceivable, 
I can conceive with ease.” What is the student to do ? The 
process is entirely a subjective one, and there is a possibility 
of his being wrong. If any defect of mind exists which 
prevents a clear comprehension of the matter, this defect 
may as easily be present in the student as in the mind of his 
critic, and who is to deliver judgment ? 
Thus Professor Poynting says: “The expansion of a 
continuous solid is unlike anything else, and is therefore 
inexplicable, but I hold—and here I think Mr. Spencer 
would consider me quite hopeless—that there is no difficulty 
in conceiving of the expansion of continuous matter.” Here 
is an apparent deadlock of the kind just described, but when 
examined it will be seen that a conception of this character 
does not hold when stated in plain terms. For Coke says 
that he could conceive a world in which two and two do not 
make four, and, extraordinary as this sounds, it is, I venture 
to suggest, an exactly parallel case, and equally valid with the 
“ expansion of a continuous solid.” The latter is verbally 
intelligible, but has it any deeper meaning ? Is it not, in fact, 
one of those illegitimate symbolic conceptions which Mr. 
Spencer defines as “ such that no cumulative or indirect 
processes of thought can enable us to ascertain that there are 
corresponding actualities, nor any predictions be made that 
can prove them ? ” 
Professor Poynting also contends that, while Mr. Spencer 
holds that the Indestructibility of Matter and the Continuity 
of Motion are necessary truths, he thinks it conceivable that 
they are false. For instance, of course, we can never be 
certain that we are right. Our conclusions are arrived at and 
tested by the only instrument at our disposal, our consciousness 
(upon the validity of which we stake ail), and may not 
correspond in the remotest degree with actual realities and 
absolute truths ; but, though the professor avers he can conceive 
these great doctrines false, surely he cannot conceive their 
opposites. We may be wrong in saying that matter is 
indestructible, but can he render into thought its destructibility, 
or can he form a conception of the annihilation of motion, or, 
in other words, of something becoming nothing ? 
