cogitation vs soul-searching

cogitation

noun
  • The process of cogitating; contemplation, deliberation, reflection, meditation. 

  • A carefully considered thought, idea, notion. 

soul-searching

noun
  • Probing introspection; a critical consideration of one's conscience; also, an instance of such consideration. 

adj
  • Involving probing introspection, or a critical consideration of one's conscience, especially motives and values. 

How often have the words cogitation and soul-searching occurred in a corpus of books? (source: Google Ngram Viewer )