In its ordinary sense the word "crowd" means a gathering of individuals of whatever nationality, profession, or sex, and whatever be the chances that have brought them together. From the psychological point of view the expression "crowd" assumes quite a different signification. Under certain given circumstances, and only under those circumstances, anagglomeration of men presents new characteristics very different from those of the individuals composing it. The sentiments and ideas of all the persons in the gathering take one and the same direction, and their conscious personality vanishes. A collective mind is formed, doubtless transitory, but presenting very clearly defined characteristics. The gathering has thus become what, in the absence of a better expression, I will call an organised crowd, or, if the term is considered preferable, a psychological crowd. It forms a single being, and is subjected to the Law of the Mental Unity of Crowds.
It is evident that it is not by the mere fact of a number of individuals finding themselves accidentally side by side that they acquire the character of an organised crowd. A thousand individuals accidentally gathered in a public place without any determined object in no way constitute a crowd from the psychological point of view. To acquire the special characteristics of such a crowd, the influence is necessary of certain predisposing causes of which we shall have to determine the nature.
The disappearance of conscious personality and the turning of feelings and thoughts in a definite direction, which are the primary characteristics of a crowd about to become organised, do not always involve the simultaneous presence of a number of individuals on one spot. Thousands of isolated individuals may acquire at certain moments, and under the influence of certain violent emotions - such, for example, as a great national event - the characteristics of a psychological crowd. It will be sufficient in that case that a mere chance should bring them together for their acts to at once assume the characteristics peculiar to the acts of a crowd. At certain moments half a dozen men might constitute a psychological crowd, which may not happen in the case of hundreds of men gathered together by accident. On the other hand, an entire nation, though there may be no visible agglomeration, may become a crowd under the action of certain influences...