268 PSYCHOLOGY AND PREACHING
obsess groups of people, and, by upsetting the control of rea son, lead to absurdity, folly and even immorality of conduct. Among the less extreme and quite healthy types belong gen uine religious revivals, which are never irrational and always ethical ; educational enthusiasms ; popular indignation at po litical corruption, such as not long since swept the United States ; agitations against gross miscarriages of justice, such as stirred the French people and the whole world in con nection with the celebrated Dreyfus case; and I should in clude also a war spirit which is inspired by genuine patriot ism or devotion to liberty and justice, though it may easily degenerate into an epidemic of the unhealthy type. In gen eral it may be said that popular excitements which have their origin in the stimulation of the higher sentiments nearly always give the population a common orientation to ward healthy action ; and, unless corrupted by some baser emotion and degraded from their ethical character, cannot leave behind them the moral devastation always found in the wake of the more extreme, irrational and unethical types of mental epidemics. Even the Crusades are not an excep tion to this ; for while there was much extravagant absurdity, from the modern point of view, connected with them, they were motived by the highest sentiment of which the peo ple of that day were capable.
I. We should bear in mind that mental epidemics are the result of two fundamental processes which are present in all social action. First, the like response to stimuli by like- minded persons. People of a similar mental organization respond in similar ways to the same stimuli ; people of un like mental organization respond to the same stimuli in dif ferent ways. We have no other way of measuring their mental likeness and unlikeness. This is too obvious to re quire any elaboration. The second process is the communi cation of mental states from one to another. This process is not so simple in the phenomena we are now discussing as it is in assemblies. The group as a whole does not assemble, though the assembling of small companies within the general
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