8 
spencer’s 
FIRST PRINCIPLES 
Jan., 1889. 
t i 
cannot by experiment prove it. We cannot show that it 
rests on any other truth. All reasoned out conclusions must 
rest on some postulate. We go on merging derivative truths 
on wider and wider truths, until at last we reach a widest 
truth which can be merged in no other or derived from no 
other. And whoever contemplates the relation in which it 
stands to the truths of science in general will (he says) see 
that this truth transcending demonstration is the persistence 
of force. 
It is remarkable that so calmly and closely reasoned an 
argument should have excited so much heat as this has done 
in certain physicists: all the more remarkable in that 
physicists have not, for the most part, closely examined the 
foundations of their great generalisation for themselves, have 
not clearly realised what is the result of experience and what 
is metaphysical assumption. Perhaps it is from this very 
neglect of the subiect that some of their bitterness towards 
8pencer has arisen. It is not pleasant to have a stranger 
coming in to set one’s house in order. But there is, I think, 
another reason. The physicists have by toilsome steps been 
pushing into a hitherto unknown country ; they have been 
drawing careful maps describing the details of its features as 
they came to them, and now after putting together the results 
obtained by generations of explorers, they have found the 
course, as it were, of the great mountain ranges and rivers. 
But Mr. Spencer seems to say that after all they need not 
have toiled so much. From the border of the country the 
general lie of the strata might have been made out, and it 
might have been seen that the mountains and rivers could 
not run otherwise than they do. And indeed all their 
survey depended on a base line at the border; all the boasted 
measures were but in terms of that base line, so that all their 
maps were but repetitions of it. It is always irritating to be 
told that if you had only kept your eyes open you might have 
saved your pains. An implication of unwisdom is always the 
direst insult. 
But after all, Mr. Spencer may not be right. For my own 
part, I share the view of the physicists, that his arguments 
are to a great extent unsound. I hold that the field of science 
cannot be mapped with certainty from its borders, and that 
our knowledge of its main features is due solely to the 
explorers. Further, in that these explorers are fallible, 
I hold it possible that their maps may be wrong, at least to 
some extent, and that future generations may show that we 
have been too hasty in assuming that we knew even the 
position of the main features. 
