skepticism vs unbelief

skepticism

noun
  • Doubt or disbelief of religious doctrines 

  • The practice or philosophy of being a skeptic. 

  • The doctrine that absolute knowledge is not possible 

  • A studied attitude of questioning and doubt 

  • A methodology that starts from a neutral standpoint and aims to acquire certainty though scientific or logical observation. 

unbelief

noun
  • An absence (or rejection) of belief, especially religious belief 

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