Crowd behaviour

S’il faut choisir un crucifié, la foule sauve toujours Barabbas.
—Jean Cocteau, Le Coq et l’Arlequin, Éditions de la Sirène, 1918

Both Socrates and Plato had good reason to be wary, or frightened, of crowd behaviour. See earlier post:

Socrates in conversation with Adeimantus:
“Do you hold, with the multitude, that there are certain individuals corrupted by sophists in their youth, and certain individual sophists who corrupt in a private capacity to any considerable extent? Do you not rather think that those who hold this language are themselves the greatest of sophists, training mostly elaborately, and finishing to their own liking, both young and old, men and women?”
“Pray when?”
“Whenever they crowd to the popular assembly, the law courts, the theatres, the camp, or any other public gathering of large bodies, and there sit in a dense and uproarious mass to censure some of the things said or done, and applaud others, always in excess; shouting and clapping, till, in addition to their own noise, the rocks and the place wherein they are echo back redoubled the uproar of their censure and applause. At such a moment, how is a young man, think you, to retain his self-possession? Can any private education that he has received hold out against such a torrent of censure and applause, and avoid being swept away down the stream, wherever it may lead, until he is brought to adopt the language of these men as to what is honourable and dishonourable, and to imitate all their practices, and to become their very counterpart?”
“It is the sure consequence, Socrates.”
—Plato, Republic, VI.492. Translation by Davies and Vaughan, Macmillan, 1852
For the Greek text, see Texts menu.

Charles Mackay, also in 1852:
Men, it has been well said, think in herds; it will be seen that they go mad in herds, while they only recover their senses slowly, and one by one…
Popular delusions began so early, spread so widely, and have lasted so long, that instead of two or three volumes, fifty would scarcely suffice to detail their history.
—Charles MacKay, Preface to Extraordinary Popular Delusions and the Madness of Crowds, Office of the National Illustrated Library, 1852.

A crowd seems on occasion to behave spontaneously, but its actions are not always pernicious: the throngs that gathered to depose Marcos in the Philippines and Ceausescu in Romania are agreed to have done a service to their country. It is yet unclear whether the phenomenon of electronic crowd-gathering can operate to similar effect.