Necessary illusion (n.) is Reinhold Niebuhr's name for the faith that keeps the ordinary person moving; rationality belongs to the cool observers who supply it.
Necessary illusion (n.) are what prevail once the inconvenient facts have become of interest only to archivists.
Necessary illusion (n.) lay the groundwork for violence: before force can be used, the public must be conditioned by propaganda to believe in the menace it is meant to meet.
A Necessary illusion (n.) survives being false in every particular: once it is established, the other side can be punished for breaking pledges it never made.
Necessary illusion (n.) are what the cool-headed few supply to the average man, whose stupidity they must recognize, to keep him on course.