Double possessive wallace

Double possessive wallace
 

-Wallace's voice is that of a hip polymath's, [...]

1. What's a hip polymath?

2. Why that and 's used together?

Here, 'that' is a relative pronoun. Its antecedent is 'voice'. It serves to make the connection between Wallace's voice and the voice of the polymath (a person of great and varied learning). 'Hip' is slang for 'informed about the latest ideas/developments'.

Thank you. But in that case do you think 's is redundant? as that already has that meaning.

Yes, the genitive ending isn't needed.

Thank you.