inwardness has 15 distinct synonyms spread across 2 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is outwardness.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the choicest or most essential or most vital part of some idea or experience
“the gist of the prosecutor's argument”
preoccupation especially with one's attitudes and ethical or ideological values
“the sensitiveness of James's characters, their seeming inwardness”
the quality or state of being inward or internal
“the inwardness of the body's organs”
preoccupation with what concerns human inner nature (especially ethical or ideological values)
“Socrates' inwardness, integrity, and inquisitiveness”
Synonyms, antonyms and the broader and narrower relations for inwardness come from Princeton University’s WordNet. Full sources and licences.