"The best that you can know, you cannot tell to boys"

  A line from Part I of Faust, a metaphysical tragedy by German polymath Johann Wolfgang von Goethe (1749-1832).  Like most of the lines Freud quotes it is spoken by the demon Mephistopheles, who speaks and acts on behalf of Satan (See note to page 65)

 

Online text of Faust: The First Part of the Tragedy, (first published 1808)