396 PROFESSOR ALISON’S DEFENCE 
stead of straining the principles of other sciences formerly ascertained, to make 
them include phenomena admitted to be distinct from any of those to which they 
have formerly been applied,—it becomes our duty to attempt the investigation 
and determination of laws peculiar to ‘iis department of nature. If these laws 
shall ultimately resolve themselves into any previously known and more general 
laws of nature, science will be simplified, and a great advance made; but it is 
assuredly mistaking the right order of inquiry to assert that, because such simpli- 
jication may ultimately be effected, therefore we are now to decline giving these 
phenomena an appropriate name, and endeavouring to reduce them to general 
laws by an induction limited to this department of nature itself. 
This is the principle which has been successfully followed in other departments 
of science. Speculations have been hazarded as to the cause of the principle of 
Gravitation itself. I recollect that the late Mr PLayrair used to say a few words 
in favour of one of these, the theory of Ultra Mundane Particles continually 
moving in all directions through all space, although not making themselves 
known to the human senses; which, if admitted, would resolve the principle of 
gravitation into that of motion communicated by impulse. But no one will main- 
tain that it was incumbent on Newron to prove, that this theory would not ex- 
plain the phenomena, before asserting the principle of gravitation, and determin- 
ing, by observation and experiment, the laws according to which that principle 
acts, or by which the phenomena coming under that head are regulated. It is, 
indeed, observed in many departments of science, that one great difficulty in the 
early inquiries is, to keep the inquirers from deviating into lines of research which 
they may think analogous to their own, and applying prematurely principles 
which have been established by an induction of very different facts. This is the 
error which Dr Rep made an object of special remark when speaking of the 
“enumeration of the original powers and laws of our mental constitution.” 
«Success in an inquiry of this kind it is not in human nature to command ; but 
perhaps it is possible, by caution and humility, to avoid error or delusion. The 
labyrinth may be too intricate to be traced through all its windings; but if we 
stop when we can trace it no farther, and secure the ground we have gained, there 
is no harm done ;-a quicker eye may in time trace it further.” —(Hamilton’s edition 
of Reid, p. 40.) In physiology itself, it is a similarly just and comprehensive obser- 
vation of Mr Lawrence, “that although organised bodies are subjected in many 
respects to physical laws, yet, as regards their own peculiar phenomena, the refer- 
ence to gravity, to attraction, to chemical affinity, to electricity or galvanism, 
can only serve to perpetuate false notions in physiology, and to draw us away 
from the proper point of view in which the nature of living phenomena, and the 
properties of living beings, ought to be considered.’’—(Zwo Introductory Lectures, 
p-. 161.) It was the same idea, not, perhaps, so accurately conceived, but more 
graphically announced, which prompted Dr Wixi1am Hunrer’s remark, in com- 

