f an invention appears to be a natural basis
of classification. It is apparent, however, that most inventions may
contribute to numerous utilities besides the ultimate one. Many
processes and instruments intervene between the seed planter and the
wheaten rolls upon the breakfast table. The plow may be viewed as an
agricultural instrument or as an instrument of civil engineering,
according as it is used for preparing the field for planting or rounding
a road. A radiating coil of pipe may be thought of as a condenser of
steam or of alcoholic vapors, according as it is applied to one material
or another; as a cooler or a heater, according to the temperature of a
fluid circulated through it. A hammer may drive nails, forge iron, crack
stone or nuts. Underlying all of these ulterior utilities, there is a
fundamental one to which the normal mind will reach in its natural
processes and there rest. The plow loosens or turns over the surface of
earth; the coil effects an exchange of heat between its interior and
exterior; the hammer strikes a blow. A classification of plows in
agriculture, road building, or excavating, according to stated ultimate
use; of a radiator coil as a steam condenser, still, jacket-water
cooler, refrigerator, or house heater; of the hammer as a forging tool,
a nail driver, or a nut cracker, appears to separate things that are
essentially alike. But classifying a plow on its necessary function of
plowing, a radiator on its necessary function of exchanging heat, a
hammer on its necessary function of striking a blow, evidently results
in getting very similar things together. Assuming for the moment that
utility is a reasonable basis of division of the useful arts, it is
deemed more logical to adopt as a basis some utility that _must_ be
effected by the means under consideration when put to its normal use
rather than some utility that _may_ be effected under _some_ conditions.
Two of the five predictables of ancient logic are property[4] and
accident.[5] The capacity of the hammer to strike a blow, the capacity
of the radiator coil to exchange heat, are in the nature of properties.
The capacity of the hammer to crack nuts, of the coil to condense steam,
are in the nature of accidents--something that follows from the impact
and the heat exchange because of the particular accidental conditions of
operation. To select an accident as a basis of classification is
contrary to the laws of thought.

It may be said t