Pro is a type of Argument. Pro is a synonym of Advantage. Advantage is related to Good. God is etymologically related to Good. 
Shade is related to Head. Head is the opposite of Tail. 
Argument <--IsA-- Pro <--Synonym--> Advantage <--RelatedTo--> Good <--EtymologicallyRelatedTo-- God 
Shade <--RelatedTo--> Head <--Antonym--> Tail 