belief vs idea

belief

noun
  • The quality or state of believing. 

  • Mental acceptance of a claim as true. 

  • Religious faith. 

  • One's religious or moral convictions. 

  • Faith or trust in the reality of something; often based upon one's own reasoning, trust in a claim, desire of actuality, and/or evidence considered. 

  • Something believed. 

idea

noun
  • A vague or fanciful notion; a feeling or hunch; an impression. 

  • An abstract archetype of a given thing, compared to which real-life examples are seen as imperfect approximations; pure essence, as opposed to actual examples. 

  • A conception in the mind of something to be done; a plan for doing something, an intention. 

  • A purposeful aim or goal; intent 

  • A musical theme or melodic subject. 

  • More generally, any result of mental activity; a thought, a notion; a way of thinking. 

  • An image of an object that is formed in the mind or recalled by the memory. 

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