A face split down the middle with Hyde on one side and Jekyll on the other.

The duality of human nature is the main theme of the novel. This is the idea that every human being has good and evil within them.

Stevenson shows this duality in the novel with Dr Jekyll's experiment, but we learn that ultimately what is important is how you behave and the decisions that you make. This determines whether a person is good or not.

Jekyll's experiment is at the heart of this theme. He seeks to separate these sides of human nature and rid himself of the evil one. Dr Jekyll comes to represent the good side of human nature while Mr Hyde represents the evil side.

The tipping point of the story comes when Hyde murders Sir Danvers Carew. Evil triumphs over good and Jekyll loses control over the opposing sides of his nature. As the novel progresses Stevenson shows us that Jekyll's idea will not work and that these opposing sides are dependant on each other to some extent.

This duality is also shown in his portrayal of London. Victorian London is portrayed as a world split into two halves with bright and grand squares contrasting with seedy back streets. This is best shown in Dr Jekyll's house which has a grand façade but a neglected and grubby back door.

"I learned to recognise the thorough and primitive duality of man."Jekyll discusses the idea of duality. He considers it "primitive" and part of man's essential nature.
"The street shone out in contrast to its dingy neighbourhood".An example of the theme of duality symbolised in the description of the city.
"I have been doomed to such a dreadful shipwreck: that man is not truly one, but truly two."Jekyll recognises the duality of human nature and recognises that this will ultimately destroy him.