Unable is the opposite of Possible. Possible is related to Realistic. Realistic is related to Real. Real is the opposite of Artificial. 
Dignity is related to Self. Self is a type of Consciousness. Consciousness is a synonym of Knowledge. 
Unable <--Antonym--> Possible <--RelatedTo--> Realistic <--RelatedTo--> Real <--Antonym--> Artificial 
Dignity <--RelatedTo--> Self --IsA--> Consciousness <--Synonym--> Knowledge 