66 
The Course of Nature. 
[January, 
As one mode of expression, we might say that modern 
science introduces into the higher modes of thought about 
nature that same kind of practical good sense which cha- 
racterises the successful man of business. Scientific inves- 
tigation is, in a certain sense, purely practical in both its 
methods and its aims. There is a mental operation, with 
which all are well acquainted, under the familiar term 
“theorising;” to this operation all scientific investigation 
is so much opposed that the mere theoriserand essayist can 
never make any real advance in the knowledge of nature. 
To speak with a little more precision, we may say that as 
science only deals with phenomena and the laws which 
conned them, so all the terms which it uses have exad 
literal meanings, and refer only to things which admit of 
being perceived by the senses, or, at least, of being con- 
ceived as thus, perceptible. This purely literal meaning 
of all scientific language is in strong contrast to the 
metaphorical and poetical forms of expression into which 
we are apt to fall in discourse upon abstrad subjeds gene- 
rally, where our ideas cannot be at once referred to sen- 
suous impressions. 
We might also say that no question is a scientific one 
which does not in some way admit of being tested by expe- 
rience. The single objed of scientific research is to predid 
the course of nature, or the results of those artificial combi- 
nations of causes which we call experiments ; and no ques- 
tion is a scientific one unless its solution will in some way 
advance this objed. I must not, however, be understood 
as saying that the test of experience can always be immedi- 
ately applied, because then no disputed question could be a 
scientific one. For example, the question whether man 
existed on the earth 50,000 years ago is a scientific one, be- 
cause it is one respeding adual historic occurrence of 
scenes evident to the senses. It could at once be settled by 
simple inspedion, could we in any way form a pidure of 
the earth as it then looked, and it may adually be settled 
in the future by the presence or absence of sensible traces 
of the existence of man at those times. Should we, however, 
go farther, and enquire whether such men had souls, our 
enquiry would not be a scientific one, nor one in which 
science could in any way concern itself with profit. The 
soul can neither be seen nor in any way made evident to 
the senses of others. From the very nature of things, it 
could leave no material trace of itself to be unearthed by 
the geologist or antiquarian of a future age. So far are we 
from forming any conception even of our own souls, as sen- 
