VOLITION 
113 
As regards inhibitory volitions, the correspondence is 
even more marked. Mr. Lewes states as follows what he 
calls the “Laws of Discharge and Arrest”:—“The 
simultaneous influence of several stimuli, each of which 
excites the same centre, is cumulative ; stimuli then assist 
each other, and their resultant is their arithmetical sum. 
Simultaneous stimuli, each of which excites a different 
centre, interfere with each other’s energy, and their resultant 
is their algebraical sum.”* Thus, a reflex action may be 
inhibited by the stimulation of a sensory nerve, even when 
the cerebrum is removed. In a frog from which the hemi¬ 
spheres have been taken, stimulation of the optic lobes and 
optic thalami delays the reflex action; and a like effect is 
produced by stimulation of any afferent nerve. “ If the fore¬ 
leg of a headless frog be irritated, the hind leg will also be 
moved by the stimulation, or vice versa. Here, then, has been 
a propagation of the excitation in either direction. But 
if while the legs are thus irritated, and the centres are ready 
to discharge, another and more powerful irritation reach the 
centre—say by pinching the skin of the back—there will be 
no discharge along the legs.”! In these and similar instances 
it is evident that inhibition may take place either because the 
opposing stimulus is the stronger, or because the path for the 
action which it initiates is better worn, though doubtless 
the latter case occurs more frequently in the higher and less 
completely mechanised centres than in the lower ones. 
I have now completed my attempt to answer the question 
with which this paper began—“What is a voluntary action?” 
—and have only to sum up results. I have tried to show that 
actions may be classified as “ automatic ” and “ impulsive ” ; 
the former being characterised by definiteness, the latter by 
variability, and hence apparent spontaneity. There is no 
separate physiological class of “voluntary” action, although 
in the regions of psychology, such a class may still be 
admitted. Such actions always seem in a peculiar sense our 
own, and, as we say, the product of our own free will, because 
the sense of effort which distinguishes them brings more 
prominently into consciousness the mental factor, as opposed 
to the mere stimulus, which, in effortless automatic and 
impulsive actions, seems to carry all before it. 
As Dr. Johnson said, “We feel we are free, and there's 
an end on't ”—or, if we are not willing that there should be 
such a summary end, we must content ourselves with the 
knowledge that our actions are free in the only intelligible 
* “ Physical Basis of Mind,” Problem II., cli. viii. 
t Ibid. 
