On Scientific Method. 
[Oddober, 
496 
implies coercive power. But are we justified in doing this ? 
To say that the law must hold good in all cases implies in- 
finite knowledge : we may have proved the law to apply in 
every instance which we have examined, but there is the 
chance that in the next instance it will fail. Prof. Jevons 
shows that “ no finite number of instances can warrant us 
in expecting with certainty that the next instance will be of 
like nature.” Every fresh instance of like nature to the pre- 
ceding increases the probability that the law will hold good 
in all instances, but after all it is only a probability that we 
have gained. “ The laws of Nature, as I venture to regard 
them, are simply general propositions concerning the corre- 
lation of properties, which have been observed to hold true 
of bodies hitherto observed. On the assumption that our ex- 
perience is of adequate extent, and that no arbitrary inter- 
ference takes place, we are then able to assign the probability, 
always less than certainty, that the next object of the same 
apparent nature will conform to the same law.”* 
We speak of matter obeying the law of gravity. In this 
proposition we imply the existence of two things — matter 
and force ; matter, a something, added on by another something, 
force. Of these two things we cannot give very good defini- 
tions. Matter is “ that which can be added upon by, or can 
exert force ;” and force is “ any cause which tends to alter 
a body’s natural state of rest, or of uniform motion in a 
straight line.’T But the force of gravity adding on particles 
of matter does not necessarily cause the adtual approach of 
one body towards another ; the addion of this force upon a 
given particle of matter is conditioned by the number, mass, 
distance, and relative position of all the other particles of 
matter within the hounds of space at the instant in question. 
We must not forget that the addion of the laws of Nature 
upon the matter of the universe is dependent upon the 
collocations (as Dr. Chalmers expressed it) of that matter at 
any moment of time. Given the same laws and the same 
mass of matter, but let the initial collocations of that matter 
vary, then the results would be altogether different for each 
collocation. No single law of Nature can be supposed to 
add independently of other laws. Every law is conditioned 
in its addion by other laws. Or, perhaps, we should say 
that, in our ignorance, we are obliged to speak of special 
laws adting and readding upon one another, when to infinite 
knowledge all would appear as under the control of but one 
* Principles of Science, vol. ii., p. 431. 
f Thomson and Tait, The Oxford Pamphlet, pp, 53, 54, 
