4 PRESIDENTIAL ADDRESS. 
statement of the conclusions to which I have been led, and 
so, I hope, enable each of you to form his own opinion of 
their value. 
THE GRowTH oF NaTuRAL PHILOSOPHY. 
Ever since the dawn of the human intellect, man has tried 
to increase his knowledge in two ways, by observation and by 
speculation. Observation came first, for that is common to 
man and animals. Speculation is a distinctly human at- 
tribute, and we find that it soon out-distanced observation, 
and formed the basis of the earlier philosophies. But, during 
the last few centuries, the observational method has once 
more come to the front, under the name of science, and its 
conclusions have not always been in accord with those of 
the speculative philosophies which preceded it. 
The difference between the two methods is that, whereas 
speculation starts a chain of reasoning from one or two pro- 
positions which are taken as absolutely true, science reasons 
from the basis of as large a number of observations as pos- 
sible, and tries to find a hypothesis which connects them 
all together, or explains them, as it is usually called. 
Evidently, this scientific process is a very laborious one, 
but it is to be more trusted than speculation. For we can 
never be certain that any single proposition is quite true, or 
that it contains the whole truth; and, as it is impossible to 
allow for modifying circumstances, reasoning alone may lead 
us far astray. While, with the scientific method, attention is 
directed to errors of observation, which can be corrected, 
and new facts are constantly confronting us which tend to 
prove, or to disprove, or to modify, our theories. These 
theories, in time, get established as what we call “laws of 
Nature’; that is, accurate records of observed cause and 
effect, and they thus form a touchstone of exact knowledge 
by which the speculative philosophies must be tried. 
No doubt, these two processes of observation and specula- 
tion went on in a desultory, impulsive manner for several 
thousands of years, during which man not only learnt a 
great deal about the material world, but was led to specu- 
late about the immaterial, or spiritual, world, which he be- 
lieved to encompass him on all sides. | We can never know 
with certainty how the conception of an invisible, spiritual 
world arose in the human mind; but we know, as a matter 
of fact, that it did do so at an early stage of the human 
intellect. Judging from the beliefs now held by the lowest 
races of mankind, it seems probable that when man first be- 
gan, in an incoherent manner, to speculate on himself and 
his surroundings, the remarkable facts connected with sleep 
