enlightenment vs free speech

enlightenment

noun
  • An act of enlightening, or the state of being enlightened or instructed. 

  • A concept in spirituality, philosophy and psychology related to achieving clarity of perception, reason and knowledge. 

free speech

noun
  • Expressions that are or should be allowed in some moral or legal context. 

  • The right to express an opinion in public without being restrained or censored. 

How often have the words enlightenment and free speech occurred in a corpus of books? (source: Google Ngram Viewer )