ted to characterize groups, whereby the
individuals of any group will resemble each other for the purpose in
view more closely than any individual in any group will resemble any
individual in any other group.

"There is no property of objects which may not be taken, if we please,
as the foundation for a classification or mental grouping of those
objects, and in our first attempts we are likely to select for that
purpose properties which are simple, easily conceived, and perceptible
in a first view without any previous process of thought--but these
classifications are seldom much adapted to the ends of that
classification which is the subject of our present remarks." (J. S.
Mill, System of Logic.)

It is clear that a number of objects may be classified on several
different bases. For example, a number of books could be divided into
groups (1) according to the subject of their contents; (2) according to
the language in which the books are written; (3) according to the size
of page; (4) according to the binding material; or (5) according to the
color of the binding. Each of these may be useful classifications for
some purpose. For the student of literature none is of value except the
first; for the connoisseur in bindings, only the last three. A
classification of animals including classes of land animals and water
animals would hardly suit a student of zoology, as it would associate
with the shad and perch such differently organized creatures as the
porpoise, whale, and seal. Yet such a classification might prove very
suitable for a student of fisheries.

_Art as a basis._[1]--So in seeking a basis for a patent office
classification the purposes of the classification should be the guide.
Allegations of ulterior uses[2] (such as may be made merely because the
inventor thought of applying his invention to those uses only, or in an
effort to get the application examined in a certain division) and other
superficial bases should be avoided. That basis will best suit the
purpose which effects such an arrangement as will exhibit in suitable
groups the "state of the prior art," by which is here meant not
necessarily all the instruments of a trade or industry, or all the
articles sold by a shopkeeper, as a stationer, but those means that
achieve similar results by the application of similar natural laws[3] to
similar substances.

As all inventions are made with the ultimate object of satisfying some
human desire, the utility o