Adolph Hitler, Mein Kampf, Vol. 1, Chapter 6, War Propaganda
What is propaganda? Propaganda is a weapon, and a frightful one in the hand of an expert. Is propaganda a means or an end? It is a means that takes a form that supports the end that it serves.
To whom should propaganda be addressed? It must be addressed always and exclusively to the masses.
The function of propaganda lies in calling the masses' attention to the significance of certain facts, processes, necessities, etc. The whole art consists in doing this so skillfully that everyone will be convinced that the fact is real, the process necessary, the necessity correct. But its effect must be aimed at the emotions and only to a very limited degree at the intellect.
The art of propaganda lies in understanding the emotional ideas of the great masses and finding, through a psychologically correct form, the way to the attention and thence to the heart of the broad masses. The ideas must be popular and their intellectual level adjusted to the most limited intelligence among those it is addressed to. Consequently, the greater the mass it is intended to reach, the lower its purely intellectual level will have to be.