Excerpt from Adolf Hitler's Mein Kampf: 
 
The function of propaganda does not lie in the
scientific training of the individual, but in calling
the masses' attention to certain facts, processes,
necessities, etc., whose significance is thus for the
first time placed within their field of vision. 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, etc. But
since propaganda is not and cannot be the necessity in
itself, since its function, like the poster, consists
in attracting the attention of the crowd, and not in
educating those who are already educated or who are
striving after education and knowledge, its effect for
the most part must be aimed at the emotions and only
to a very limited degree at the so-called
intellect...The more modest its intellectual ballast,
the more exclusively it takes into consideration the
emotions of the masses, the more effective it will
be..."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 receptivity of the great masses is very limited,
their intelligence is small, but their power of
forgetting is enormous. In consequence of these facts,
all effective propaganda must be limited to a very few
points and must harp on these slogans until the last
member of the public understands what you want him to
understand [or believe]..."The war propaganda of the
English and Americans were psychologically sound. By
representing the Germans to their own people as
barbarians and Huns, they prepared the individual
soldier for the terrors of war, and thus helped to
preserve him from disappointments. After this, the
most terrible weapon that was used against him seemed
only to confirm what his propagandists had told him;
it likewise reinforced his faith in the truth of his
government's assertions, while on the other hand it
increased his rage and hatred against the vile enemy
For the cruel effects of the weapon, whose use by the
enemy he now came to know, gradually came to confirm
for him the 'Hunnish' brutality of the barbarous
enemy, which he had heard all about; and it never
dawned on him for a moment that his own weapons
possibly, if not probably, might be even more terrible
in their effects..."The function of propaganda is, for
example, not to weigh and ponder the rights of
different people, but exclusively to emphasize the one
right which it has set out to argue for. Its task is
not to make an objective study of the truth, in so far
as it favors the enemy, and then set it before the
masses with academic fairness; its task is to serve
our own right, always and unflinchingly...The broad
mass of a nation does not consist of diplomats, or
even professors of political law, or even individuals
capable of forming a rational opinion; it consists of
plain mortals, wavering and inclined to doubt and
uncertainty. As soon as our own propaganda admits so
much as a glimmer of right on the other side, the
foundation for doubt in our own right has been laid.
The masses are then in no position to distinguish
where foreign injustice ends and our own begins."