CHAPTER XII
MENTAL EPIDEMICS
THE term " epidemic " has been so closely associated with morbid phenomena of a certain type that one hesitates to use it to designate the class of mental experiences here to be discussed. But the lack of a better word will justify its use.
A mental epidemic is the sweep of a common emotional excitement over a whole social group. The group may be a neighbourhood, a city, a nation, a party, a sect, a class, a sex, or any other well denned and relatively permanent segment of the population which has some common interest and some means of frequent intercommunication. Through such a group are all the time flowing mental currents which main tain its unity of thought and feeling and its collective indi viduality. Without such a constant flow of ideas and senti ments the group would disintegrate, just as the physical or ganism would decompose if the circulation of the blood were to stop. However, the term mental epidemic is not applied to the regular processes by which mental unity is maintained, but only to those waves of emotion which give the people a more intensive unity than the ordinary.
There are two broad classes of mental epidemics between which the distinction should be emphasized. As in a crowd the fusion may be more or less complete, and injurious or healthy accordingly, so the mental unity induced in the larger group may be only what is necessary to insure con certed and vigorous action under the control of intelligence ; or it may become so passionate, so overwhelming in emo tional intensity, as to be demoralizing even when the excite ment centres about some unobjectionable or really important interest. To the more intense forms of such excitement the terms, " popular mania " or " craze," should be applied. It
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