Gustave Le Bon 
The French Revolution and the Psychology of Revolution [PDF ebook] 

In his discussion of the general psychological causes of revolution, Le Bon draws detailed illustrations of fundamental points from the French Revolution, especially the period from 1789 to 1800. Le Bon»s treatment of psychological causes is not confined to crowd actions or to the immediate descriptions of violent episodes in revolutions. He draws upon contemporary French clinical psychology to describe the pathological characteristics of the revolutionary leadership in France and explains many of the events of the period as a consequence of their influence.