588 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
mathematical statement. I had doubted, on receiving the notice for this 
evening’s discussion, whether the subject announced strictly came within 
the province of the mathematical section. The question, “ What is force ? ” 
seemed more properly to belong to physics, and to involve one of the fun¬ 
damental definitions of Philosophy; yet 1 recognize that the subject is 
in a sense a mathematical one. Mathematicians find in their analytical 
processes certain constants and also variables, representing a rate of 
acceleration in dynamic problems, and this they conveniently term force, 
throwing causes out of view; to w T hich there is no objection. This, 
however, affords no answer to the question, “ What is force ? ” Mathe¬ 
matics is purely a science of abstract relations, dealing with such rela¬ 
tivities as number, quantity, extension, position, dimension, and time, and 
their variations, by deductive methods, and hence is incapable of replying 
to primary questions of ontology. Many mathematicians, therefore, find¬ 
ing the question irrelevant to their science, throw it out and deny that 
force has any existence other than as a mathematical expression. Perhaps 
the question cannot be answered. The word “ force,” however, exists in 
our language, as in others, as a symbol of a reality of nature, though still 
with an ambiguity of usage proportional to the abstruseness of the subject. 
It is a fact in language, as in all other evolutionary products, that function 
precedes structure and is the prime cause of the evolution of structure. Thus 
both organs and words exist at first in a generalized and rudimentary 
state, the organ or word becoming specialized as the function becomes 
differentiated. The terms of physics and mechanics have become more 
specialized within the last twenty-five years. About a quarter of a cen¬ 
tury ago a distinguished English physicist published a work which he 
called “ The Correlation of the Physical Forces,” a title not particularly 
incorrect at that time, but which now would be w r ritten “ The correlation of 
the various modes of energy; ” energy being the well-understood dynamic 
term for the manifestations of matter in motion and capable of doing 
work by transference of motion. Heat, although a form of vis impressa, 
being a mode of motion capable of impressing itself by transference, has 
been differentiated as a form of energy, as much so as vis viva. 
Force is the proximate cause of motion, while energy is the product or 
resultant compounded of mass and the variable factor motion, itself a 
function of space and time. Energy is therefore variable and transferable, 
while force is persistent and inexhaustible, and manifest as well under 
static as under dynamic conditions. A magnet or a planet draws a million 
neighboring bodies with the same power as one. Force in its centripetal 
aspect appears to exist as a universal stress and is not separately apparent. 
There is an intermolecular stress which takes the names of cohesion and 
affinity. In its aspect of mass, force is manifest under the various forms 
of “ 'vis ” as used by Newton, the basis of which is inertia or persistence 
of condition. In this aspect it is also a cause of motion by transference or 
by conservation of condition. I hold, then, that in the necessary imper¬ 
fection of language we may with propriety use the term force in either 
