Servant is the opposite of Free. Free is related to Independent. Independent is related to Autonomy. 
Voice is the opposite of Fact. Fact is related to Item. Item is a type of Part. Part is a synonym of Participation. 
Servant <--Antonym--> Free <--RelatedTo--> Independent <--RelatedTo--> Autonomy 
Voice <--Antonym--> Fact <--RelatedTo--> Item --IsA--> Part <--Synonym--> Participation 