raison d'être vs thesis

raison d'être

noun
  • Reason for being. The claimed reason for the existence of something or someone; the sole or ultimate purpose of something or someone. 

thesis

noun
  • An affirmation, or distinction from a supposition or hypothesis. 

  • In the dialectical method of Georg Wilhelm Friedrich Hegel: the initial stage of reasoning where a formal statement of a point is developed; this is followed by antithesis and synthesis. 

  • A depression of the voice when pronouncing a syllables of a word; hence, the unstressed part of the metrical foot of a verse upon which such a depression falls, or an unaccented musical note. 

  • The action of lowering the hand or bringing down the foot when indicating a rhythm; hence, an accented part of a measure of music or verse indicated by this action; an ictus, a stress. 

  • A proposition or statement supported by arguments. 

  • A lengthy essay written to establish the validity of a thesis (sense 1.1), especially one submitted in order to complete the requirements for a non-doctoral degree in the US and a doctoral degree in the UK; a dissertation. 

  • A conjecture, especially one too vague to be formally stated or verified but useful as a working convention. 

How often have the words raison d'être and thesis occurred in a corpus of books? (source: Google Ngram Viewer )