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duality, an instance of opposition or contrast between two concepts or two aspects of something; a dualism.

The theory of Duality, likewise in The Strange Case Of Dr Jekyll and Mr Hyde. Dr Jekyll takes a potion that makes him evil, blah blah blah. Dr Jekyll enjoys being his alter ego, Mr Hyde, the evil one. (I suggest you read the book, i'm reading this book for my GCSE and really enjoying it.)

What happens when Stiles has to choose.....

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