an
atom, the supposition that there are ultimate particles of matter in
which the "promise and potency" of all physical properties and actions
reside has served as a means of investigation during the most intensive
period of research in the history of thought. Without the hypothesis of
the atom, physics and chemistry, and in a secondary sense biology, would
have lacked chart and compass upon their voyages of exploration.
Although the notion of the atom is rapidly changing, and the tendency of
physical science is to construe physical facts in terms of motion rather
than of the traditional atom, it is probably as needless as it is
useless for us to concern ourselves as laymen with this refinement.
Although we cannot avoid speaking of the smallest parts into which
matter can be divided, and although we cannot imagine, on the other
hand, how any portions of matter can exist and not be divisible into
parts, we are probably quite as incapable of saving ourselves from
paradox by resort to the vortex hypothesis in any form. That is, these
subtleties are too wonderful for most minds. Without pushing analysis
too far, and without resting any theory upon analogy with the atom of
physical theory, it is necessary to find some starting-place from which
to trace up the composition of sentient beings, just as the physicists
assumed that they found their starting-place in the atom. The notion of
interests is accordingly serving the same purpose in sociology which the
notion of atoms has served in physical science. Interests are the stuff
that men are made of. More accurately expressed, the last elements to
which we can reduce the actions of human beings are units which we may
conveniently name "interests." It is merely inverting the form of
expression to say: _Interests are the simplest modes of motion which we
can trace in the conduct of human beings._

To the psychologist the individual is interesting primarily as a center
of knowing, feeling, and willing. To the sociologist the individual
begins to be interesting when he is thought as knowing, feeling, and
willing _something_. In so far as a mere trick of emphasis may serve to
distinguish problems, this ictus indicates the sociological
starting-point. The individual given in experience is thought to the
point at which he is available for sociological assumption, when he is
recognized as a center of activities which make for something outside of
the psychical series in which volition