i877-J 
On Scientific Method . 
479 
must be examined is clearly, the laws which regulate reason it- 
self, the laws of thought, and their application to the processes 
of inference. The study of these belongs to the science of Logic. 
The application of these principles to reasoning about numbers 
and quantities constitutes the science of Mathematics, and 
so on. 
We have one set of sciences dealing with physical or 
material objedts; another with mental, moral, or imma- 
terial objedts ; or with these as they are modified by 
social relationships. Hence arise the two broad classes 
of natural or material, and mental or moral science. 
The scientific method is applicable to both alike, only the 
questions arising under the second division are more compli- 
cated and much more difficult of solution than those under 
the first. Indeed it is only within recent years that the sci- 
entific method has been, in any great degree, applied to the 
questions of mental and social phenomena. 
In endeavouring to classify scientifically the phenomena of 
Nature we make use of the method, first of all, of Obser- 
vation. 
From experience we gather together a number of fadts, 
but in order to classify these fadts we need often have recourse 
to Experiment. 
In the first-named process we do not alter the conditions 
under which phenomena occur in Nature ; we merely observe 
these phenomena as they are presented to us, or at most we 
vary our point of view. In carrying out an experiment, on 
the other hand, we must carefully vary the conditions of the 
phenomenon , and endeavour, as far as possible, to exclude 
those which have no influence upon the fadt we are studying. 
Observation and experiment are the first steps in the ladder 
leading upward to scientific knowledge. 
But where are observations to begin ? In our world fadts 
are so numerous, phenomena so almost infinite in number, 
that no man can say which are to be observed and which 
negledted. Hence we find that many of the greatest scien- 
tific discoveries have taken their rise from what we call 
“ chance ” observations. But that which is passed by, by 
one man, as altogether unimportant, in the hands of another 
leads to the most important results. The twitching of the 
leg of a dead frog when accidentally touched by the wires 
coming from a battery caught the eye of Galvani, and he, fol- 
lowing up this chance observation, so added new fadts and new 
theories to our scientific stock that one of the greatest branches 
of Eledtric Science now derives its name from this man. 
It is impossible, however, to carry out the method of 
