How does a minor character in 1984 show the theme of the novel?

In 1984, Orwell uses minor characters to demonstrate the extent of the Party's control and to warn against the dangers of totalitarian regimes.

Take the character of Syme, for example, who appears in Part One, Chapter Five. Syme is a colleague of Winston's and works on the development of Newspeak, the official language of Oceania. During conversation, Syme explains the purpose of Newspeak:

We're destroying words - scores of them, hundreds of them, everyday. We're cutting the language down to the bone. 

More importantly, the purpose of this cutting-down is to control people's ability to express their thoughts. As Syme comments:

In the end, we shall make thoughtcrime literally impossible, because there will be no words in which to express it.

Syme, therefore, symbolizes the Party's domination of independent thought. What is, perhaps, more concerning is Syme's pride in such a task: he is lively and animated when describing his work to Winston and believes that the destruction of language is beautiful. In this respect, Orwell uses Syme to demonstrate the dangers of a dominated mind: Syme cannot see the inherent problems in thought control because he has been brainwashed by the Party.

We can contrast Syme with another minor character, to further understand the themes of 1984. Take, for example, the Prole woman who sings in the courtyard in Part Two, Chapter Ten. As she hangs her washing in the courtyard, Winston speculates on her life. Her appearance suggests that she has birthed many children and she, perhaps, lives in a degree of poverty in the Prole district but she represents hope and freedom. Her carefree demeanour suggests to Winston that the Proles offer the only hope of revolution against the Party. The Prole woman thus becomes an impetus for Winston's rebellion and a symbol of optimism for the future of Oceania.