illusion vs self-contradiction

illusion

noun
  • A misapprehension; a belief in something that is in fact not true. 

  • Anything that seems to be something that it is not. 

  • A magician’s trick. 

  • The state of being deceived or misled. 

self-contradiction

noun
  • A statement that contains a contradiction, or a premise from which one could be derived 

How often have the words illusion and self-contradiction occurred in a corpus of books? (source: Google Ngram Viewer )