IX LIMITS OF NATURAL SELECTION IN MAN 211 
All Force is probably Will-Force 
If we are satisfied that force or forces are all that exist 
in the material universe, we are next led to inquire 
what is force? We are acquainted with two radically 
distinct or apparently distinct kinds of force—the first 
consists of the primary forces of nature, such as gravitation, 
cohesion, repulsion, heat, electricity, etc.; the second is 
our own will-force. Many persons will at once deny that 
the latter exists. It will be said that it is a mere trans- 
formation of the primary forces before alluded to; that the 
correlation of forces includes those of animal life, and that 
will itself is but the result of molecular change in the brain. 
I think, however, that it can be shown that this latter asser- 
tion has neither been proved, nor even been proved to be 
possible ; and that in making it, a great leap in the dark has 
been taken from the known to the unknown. It may be at 
once admitted that the muscular force of animals and men is 
merely the transformed energy derived from the primary 
forces of nature. So much has been, if not rigidly proved, 
yet rendered highly probable, and it is in perfect accordance 
with all our knowledge of natural forces and natural laws. 
But it cannot be contended that the physiological balance- 
sheet has ever been so accurately struck, that we are entitled 
to say, not one-thousandth part of a grain more of force has 
been exerted by any organised body, or in any part of it, than 
has been derived from the known primary forces of the 
material world. If that were so, it would absolutely negative 
the existence of will; for if will is anything, it is a power that 
directs the action of the forces stored up in the body, and it is 
not conceivable that this direction can take place, without the 
exercise of some force in some part of the organism. How- 
ever delicately a machine may be constructed, with the most 
exquisitely contrived detents to release a weight or spring by 
the exertion of the smallest possible amount of force, some 
external force will always be required; so, in the animal 
machine, however minute may be the changes required in 
the cells or fibres of the brain, to set in motion the nerve 
currents which loosen or excite the pent-up forces of certain 
muscles, some force must be required to effect those changes. 
