In this monograph, Freud describes     at work within   . A   mass , according to Freud, is a "temporary entity, consisting of heterogeneous elements that have joined together for a moment."He refers heavily to the writings of sociologist and psychologist     (1841-1931), summarizing his work at the beginning of the book in the chapter   Like Le Bon, Freud says that as part of the mass, the individual acquires a sense of infinite     allowing him to act on     that he would otherwise have to curb as an isolated individual. These feelings of power and security allow the individual not only to act as part of the mass, but also to feel   . This is accompanied, however, by a loss of     personality and a tendency of the individual to be infected by any emotion within the mass, and to amplify the emotion, in turn, by "mutual induction". Overall, the mass is "impulsive, changeable, and irritable. It is controlled almost exclusively by the   ."