1879 -] 
The Course of Nature. 
79 
the rock from time to time, and knowing also the laws of 
molecular action between the rock and the water, could 
determine long in advance the very moment at which the 
rock would fall. 
Going back another step, we see that the quantity of water 
which runs over the rock depends on antecedent circum- 
stances in the same way, namely, upon the quantity of the 
rainfall and the arrangement of the crevices in the ground. 
However the latter may have been produced, the cause is 
still another link in the endless chain which we can trace 
back to preceding links as far as we please. Equally is the 
rainfall a fixed element, determined by the course of the 
winds and the amount of moisture which they carry. Thus 
we have a network of causes too complicated for the human 
mind to trace in detail, but which the philosophy of science 
teaches us act with mathematical certainty. No tempering, 
modifying, or adjusting action comes in at any stage of the 
process, so far as we can see ; if we admit such action we 
have to keep placing it farther back as our knowledge in- 
creases. 
Now there is one feature of these causes, the admission 
or rejection of which constitutes the main point of difference 
between the two schools of thought which I have before 
indicated. All are agreed that the course of nature is 
determined by what we may call causes or laws, but all are 
not agreed as to the scope of adtion of these laws. The 
great and distinguishing feature which the school of science 
recognises, and which the other school does not recognise, 
is that all the laws of nature adt without any scrutable 
regard to consequences. I qualify my statement by the 
word scrutable, because it is entirely outside the pale of 
scientific research to speculate upon possible inscrutable 
ends in nature. This being a subjedt of which the man of 
science, speaking as such, can affirm nothing, so he can 
deny nothing. Having found that no trace of regard for 
consequences can be seen in the mode of adtion of the laws 
which he investigates, but that the whole course of things, 
so far as his eye can penetrate, may be explained and pre- 
dicted without supposing any such regard, the demands of 
science are satisfied, and he must there stop. 
Let me illustrate this by going over the train of thought 
which has just occupied us in the opposite direction, 
starting from the rainfall, and tracing the succession of 
causes to the fall of the rock. The spot at which each drop 
of rain shall fall is determined by antecedent conditions 
entirely, by gravitation, and the winds. The drop neither 
