Among these are the necessity to cling to the existence of the father, the prolongation of earthly existence by a future life, and the immortality of the human soul. To differentiate between an illusion and an error, Freud lists scientific beliefs such as "Aristotle's belief that vermin are developed out of dung" (pg.39) as errors, but "the assertion made by certain nationalists that the Indo-Germanic race is the only one capable of civilization" is an illusion, simply because of the wishing involved. Put forth more explicitly, "what is characteristic of illusions is that they are derived from human wishes." (pg. 39)