The receptive powers of the masses are very restricted, and their understanding is feeble. On the other hand, they quickly forget. Such being the case, all effective propaganda must be confined to a few bare essentials and those must be expressed as far as possible in stereotyped formulas. These slogans should be persistently repeated until the very last individual has come to grasp the idea that has been put forward. If this principle be forgotten and if an attempt be made to be abstract and general, the propaganda will turn out ineffective; for the public will not be able to digest or retain what is offered to them in this way. Therefore, the greater the scope of the message that has to be presented, the more necessary it is for the propaganda to discover that plan of action which is psychologically the most efficient.