388 Mr. W. R. Browne on the 
pcedia, which alone supplies the evidence on which this rests, we 
find, as already mentioned, that the new conception of Force, as 
something without objective existence, is only hinted at the 
beginning, and then relegated to an appendix at the end, the 
whole of the results being developed in the ordinary manner. 
This appendix of " General Considerations " is therefore the 
place where we are at last to find the evidence we seek ; and 
here, in fact, we do find it, put in the simplest and clearest form; 
so that we are at once able to examine and estimate its value. It 
is all confined to a very few paragraphs (291-295), and may 
be expressed in the following propositions: — 
(1) We believe Matter, whatever it may be, to have an 
objective existence, chiefly because it is " conserved," i. e. 
because experiment teaches us that its quantity cannot be 
altered. 
(2) The only thing in nature which is also conserved in this 
sense is Energy. 
(3) Therefore Energy is the other objective reality in the 
physical universe; and we must look to it for information as 
to the true nature of what we call Force. 
(4) Taking as the simplest case the fall of a stone towards 
the earth, we find the equation 
|Mv 2 =WA, 
which may be interpreted as stating that the kinetic energy 
acquired is equal to the force acting multiplied by the distance 
fallen through. But if we introduce the element of time, by 
vt 
means of the relation h— -^, this equation at once becomes 
t 
(5) Hence Force appears in a new light. It is now the 
time-rate at which momentum is generated in the foiling stone. 
(6) But a mere rate, be it a space-rate or a time-rate, is 
not a thing which has objective existence. No one would 
confound the bank rate of interest with a sum of money, nor 
the birth- or death-rate of a country with a group of indivi- 
dual human beings. 
(7) Therefore Force, being a rate of generation of momen- 
tum, is not an objective reality. 
I do not think Prof. Tait can quarrel with this mode of 
stating the argument, which is mainly in his own words. It 
is a clear and connected chain of reasoning; and therefore the 
conclusion may be overthrown by overthrowing any one of the 
