heart and soul vs inwardness

heart and soul and inwardness both are nouns.

Word	Noun	Adjective	Verb	Adverb
heart and soul	Yes	No	No	Yes
inwardness	Yes	No	No	No

As nouns, heart and soul and inwardness are synonyms defined as:

heart and soul and inwardness: the choicest or most essential or most vital part of some idea or experience

Other synonyms of heart and soul include center, centre, core, essence, gist, heart, kernel, marrow, meat, nitty-gritty, nub, pith, substance, sum.

heart and soul (noun)	inwardness (noun)
the choicest or most essential or most vital part of some idea or experience	the quality or state of being inward or internal
	preoccupation with what concerns human inner nature (especially ethical or ideological values)
	preoccupation especially with one's attitudes and ethical or ideological values
	the choicest or most essential or most vital part of some idea or experience

heart and soul (adverb)	inwardness (adverb)
with complete faith