meditation vs self-questioning

meditation

noun
  • A contemplative discourse, often on a religious or philosophical subject. 

  • A devotional exercise of, or leading to contemplation. 

  • Careful and thorough thought. 

  • A musical theme treated in a meditative manner. 

self-questioning

noun
  • contemplation on one's actions, beliefs, etc. 

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