t in so far
as they prevent communication. The isolation of the mountain whites in
the southern states, even if based on spatial separation, consisted in
the absence of contacts and competition, participation in the
progressive currents of civilization.

Biological differences, whether physical or mental, between the
different races are sociologically important to the extent to which they
affect communication. Of themselves, differences in skin color between
races would not prevent intercommunication of ideas. But the physical
marks of racial differences have invariably become the symbols of racial
solidarity and racial exclusiveness. The problems of humanity are
altogether different from what they would have been were all races of
one complexion as they are of one blood.

Certain physical and mental defects and differences in and of themselves
tend to separate the individual from his group. The deaf-mute and the
blind are deprived of normal avenues to communication. "My deafness,"
wrote Beethoven, "forces me to live in exile." The physically
handicapped are frequently unable to participate in certain human
activities on equal terms with their fellows. Minor physical defects and
marked physical variations from the normal tend to become the basis of
social discrimination.

Mental differences frequently offer still greater obstacles to social
contacts. The idiot and the imbecile are obviously debarred from normal
communication with their intelligent associates. The "dunce" was
isolated by village ridicule and contempt long before the term "moron"
was coined, or the feeble-minded segregated in institutions and
colonies. The individual with the highest native endowments, the genius,
and the talented enjoy or suffer from a more subtle type of isolation
from their fellows, that is, the isolation of eminence. "The reason of
isolation," says Thoreau, a lover of solitude, "is not that we love to
be alone, but that we love to soar; and when we soar, the company grows
thinner and thinner until there is none left."

So far, isolation as a tool of social analysis has been treated as an
effect of geographical separation or of structural differentiation
resulting in limitation of communication. Social distances are
frequently based on other subtler forms of isolation.

The study of cultural differences between groups has revealed barriers
quite as real and as effective as those of physical space and structure.
Variations in lang