inner nature

38 Moby Thesaurus words for "inner nature":
      bosom, breast, center, center of life, core, deepest recesses,
      esoteric reality, heart, heart of hearts, inmost heart,
      inmost soul, inner, inner landscape, inner life, inner man,
      inner recess, inner self, inside, interior, interior man, intern,
      internal, intrados, inward, nerve center, penetralia, quick,
      recesses, secret heart, secret place, secret places, soul, spirit,
      true being, true inwardness, vital center, vital principle,
      vitals