8 PRESIDENT’S ADDRESS. 
the student finds little to disturb him, perhaps too little, 
in the idea that mass changes with velocity; and he does not 
always realise the full meaning of the consequences which are 
involved.’ 
This readiness to accept and incorporate new facts into the scheme 
of physics may have led to perhaps an undue amount of scientific 
scepticism, in order to right the balance. 
But a still deeper variety of comprehensive scepticism exists, and 
it is argued that all our laws of nature, so laboriously ascertained and 
carefully formulated, are but conventions after all, not truths: that 
we have no faculty for ascertaining real truth, that our intelligence 
was not evolyed for any such academic purpose; that all we can do 
is to express things in a form convenient for present purposes and 
employ that mode of expression as a tentative and pragmatically useful 
explanation. 
Even explanation, however, has been discarded as too ambitious 
hy some men of science, who claim only the power to describe. They 
not only emphasise the how rather than the why,—as is in some sort 
inevitable, since explanations are never ultimate—but are satisfied with 
very abstract propositions, and regard mathematical equations as 
preferable to, because safer than, mechanical analogies or models. 
“To use an acute and familiar expression of Gustav Kirchhoff, 
it is the object of science to describe natural phenomena, not to 
explain them. When we have expressed by an equation the 
correct relationship between different natural phenomena we have 
gone as far as we safely can, and if we go beyond we are entering 
on purely speculative ground.’ 
But the modes of statement preferred by those who distrust our 
power of going correctly into detail are far from satisfactory. Pro- 
fessor Schuster describes and comments on them thus :— 
‘ Vagueness, which used to be recognised as our great enemy, 
is now being enshrined as an idol to be worshipped. We may 
never know what constitutes atoms, or what is the real structure 
of the ether; why trouble, therefore, it is said, to find out more 
about them. Is it not safer, on the contrary, to confine our- 
selves to a general talk on entropy, luminiferous vectors, and un- 
defined symbols expressing vaguely certain physical relation- 
ships? What really lies at the bottom of the great fascination 
which these new doctrines exert on the present generation is 
sheer cowardice; the fear of having its errors brought home 
HO aby 3. tele 
“I believe this doctrine to be fatal to a healthy development 
of science. Granting the impossibility of penetrating beyond the 
